The Government You Paid For

Number 18

Oops! I should be more careful what I wish for. Apparently we are now getting the government we paid for, and that government would include the newly-minted FCC Chairman Ajit Pai. See the video. This is the kind of thing you would expect if you put a coin in a strange vending machine and punched one of the unfamiliar buttons on the front. Out pops the product. In this case it’s Mr. Pai explaining why ending net neutrality is such a good thing—or else maybe not so bad as your second or third impression would make it out. Just watch the video. It is required. Your tax dollars paid for it.

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Quiz Question

One of a continuing series

It’s time to quit taking these Quiz Questions seriously. Here’s one for this week.

See the above photo. What is the object pictured, and what purpose did it used to serve?

Post your answers in the comments section. It’s all right to use Google to find the answer.

Hello, I’m the 21st century, and I’m here to take your job.

technology-trace-01

TRACE, a machine that reads bank checks

I spent nearly 50 years of my life as an engineer, and I think I know when it first started. It was in 1971 that I begin to work in earnest to eliminate people’s jobs.

There was a small engineering consulting company in Austin, and we received a contract from a concern called Autotronic Systems, Inc. Ignoring the name, the company was headquartered in Houston, and they had a chain of self-service gas stations about the country. That was an innovation in 1971, pumping your own gas. It eliminated the job of the smiley attendant, who also checked your oil and wiped your windshield. Our job was to design equipment that fit inside the gas pump and recorded the amount of fuel pumped and the amount charged. The data were transmitted to another device we designed that would store daily sales data and at night phone the home office and transmit the information. Wayne van Citters and I did the software for the home office computer. People lost their jobs.

Two years later  I was working for a company in Irving, Texas, and what they did was build machinery that read the sales receipts from gas stations and did all the sales computation. Their machinery would also read bank checks, printed forms, and mail addresses on envelopes. We eliminated the jobs of the people who previously did this data entry.

In  particular, the company worked on a program to eliminate Post Office workers who eyed addresses and typed them in, or just entered the ZIP code if that was available. Twelve such work stations fed huge machines by Pitney-Bowes that then sorted the mail to the appropriate collection bins. The huge machine was appropriately call a Letter Sorter Machine (LSM). Jobs were eliminated.

I worked a few weeks at a test operation at the Post Office on 8th Avenue in Manhattan, across the street from Madison Square Garden. Postal workers did not like us. There was back room talk of workers sabotaging the machines. Eventually the company I worked for lost the contract to IBM, and I was fired. But the next day I went back  to work for them and did more mischief, eliminating jobs for several more years.

My first patent was for a machine that wrapped a band around a stack of dollar bills. It didn’t have to be one-dollar bills, it would put the strap around 100 bills of any denomination. We sold this system to the Federal Reserve Bank, and my invention eliminated the job of the person who used to put the strap on. Who wanted that job, anyway?

The same company was also a leader in the development of the ATM (automated teller machine). These machines are still around, and they have eliminated thousands of jobs in the banking industry. Docutel was the company that developed ATMs, and it was acquired by Olivetti.

Next I worked on weapons systems for the United States military. You could say I eliminated soldiers’ jobs by automating the work of killing people. My first project involved automating the location of submarines by sonar. I did the software.

My life of developing computer software aimed at eliminating the human element from all manner of tasks. My wife worked for an engineering company, and she was the business manager. She hired me to develop computer software to automate the repetitious accounting tasks. This was before the days of Quick Books.

I finally quit the business of killing jobs four years ago. It’s now the 21st century, and those jobs are not coming back. People are looking for things to do.

Donald Trump campaigned on the basis of a multitude of promises. One promise was to bring back jobs that have been lost in the coal industry. Disinterested parties have looked at this and wondered aloud who would want to go back to working in a coal mine. Nevertheless, idle miners are now looking ahead to going back underground and chewing at the coal seams, or else, sawing off the tops of mountains and scooping up the exposed coal.

But it’s not just safety and environmental concerns that are killing the coal jobs. The 21st century is killing coal jobs. Nuclear power, natural gas-fired power plants, and finally solar and wind power are killing coal jobs. These jobs are not coming back.

Progressive politicians bring us good news. Green power, they promise, will bring back the jobs lost at the coal mines. There is an enormous industry being created to produce wind turbines and solar farms. The new industry will create in the order of 100,000 new jobs, far exceeding the 30,000 lost at the mines.

Not so fast. These green power jobs are not permanent. Once the solar and wind farms are constructed and brought on-line, the industry will only need people to maintain these facilities and to expand them as power needs increase. Unlike coal, wind blows when you are not looking, and the sun comes up every morning. There is no need for the man to shovel sunshine onto a solar panel.

It’s much the same with the automobile industry. Teams of workers who used to assemble automobiles in the United States and in other countries have been replaced by robots. The major industries of electronics and computers would be impossible without the complete automation of just about all processes involved. Watch a video of computer disk drives being manufactured, and you will get an appreciation of the minuscule degree of direct human involvement.

It’s coming to be much the same in all major industries. Retail is eliminating the sales clerk who spends 30 minutes with a customer looking at a $30 pair of shoes without buying. Amazon started it with books, but the trend continues upward. The elimination of human-driven retail drives customer costs down, making it better for the economy all around, but at the cost of out-of-work sales staff.

Will there ever come a time when people will no longer need to be directly involved in producing goods and services? It’s hard to say. Many jobs I (and others) predicted would never go away are now gone for good. Economics, like nature, seeks the steady state. Eliminating jobs reduces the cost of products, but it also eliminates the customer who is supposed to pay for the products. Eventually a balance will be obtained, but at what level? In the meantime, workers are shuffling and trying to adjust, or not. The coal miners of West Virginia just defeated a candidate who promised to eliminate their jobs.

Will workers be able to vote their jobs back? Not likely. When it has been tried it has failed. Communism was a political approach to managing the economy, and it resulted in near 100% employment at the cost of dismal standards of living. This reality killed communism and the Soviet Union, but communism still thrives in the PRC, Vietnam, Laos, and Cuba. I am not mentioning North Korea, which seems to be a special case.

In conclusion, if you recently, or a long time ago, lost your job because of me, don’t bother trying to find me. First, it would not be worth your effort, and second you would be chasing the wrong perpetrator. It was the 21st century that took your job.

Friday Funny

One of a series

Airliner crosses Vineland Avenue North Hollywood while landing at Burbank Airport

Airliner crosses Vineland Avenue North Hollywood while landing at Burbank Airport

It’s Friday. There’s always something:

(CNN) — A flight to Malaysia from Sydney was diverted to Melbourne after its pilot entered incorrect coordinates of the plane’s starting position, an Australian aviation investigation report has found.

Carrying 212 passengers, the AirAsia flight bound for Kuala Lumpur on March 10, 2015, was flying in the wrong direction after takeoff from Sydney, because the pilot had manually entered the wrong coordinates of the plane’s position into the flight’s onboard navigation systems.

Isn’t modern technology wonderful. I hear the next thing they are proposing is cars that drive themselves. It’s going to be funny.

Quiz Question

One of a continuing series

History-SailingShip-01

Before GPS, before LORAN, navigators (ocean) determined their latitude by the angle between the sun and the horizon at noon. They determined their longitude by the time when the sun was highest in the sky (or when the sun came above the horizon). But to do that they needed to know what time it was.

At first they had hour glasses to tell the time, and it was the job of somebody to always watch the hour glass and to turn it when the sand ran down. Eventually expert clock makers devised ever more accurate clocks to help navigators determine their longitude. The advent of the telescope made it possible to get an accurate time reference that did not drift. How might that work?

Post your answer as a comment below.

Update and answer

See the comments below. Greg was onto the solution, but he didn’t carry it to conclusion. The answer is that the advent of telescopes enabled navigators to see the moons of Jupiter. There are four large ones that are visible to anybody with a good set of binoculars, and their motions provide a reliable time reference. Early navigators did make use of these observations to determine longitude with greater accuracy:

In 1612, having determined the orbital periods of Jupiter’s four brightest satellites (Io, Europa, Ganymede and Callisto), Galileo proposed that with sufficiently accurate knowledge of their orbits one could use their positions as a universal clock, which would make possible the determination of longitude. He worked on this problem from time to time during the remainder of his life.

To be successful, this method required the observation of the moons from the deck of a moving ship. To this end, Galileo proposed the celatone, a device in the form of a helmet with a telescope mounted so as to accommodate the motion of the observer on the ship. This was later replaced with the idea of a pair of nested hemispheric shells separated by a bath of oil. This would provide a platform that would allow the observer to remain stationary as the ship rolled beneath him, in the manner of a gimballed platform. To provide for the determination of time from the observed moons’ positions, a Jovilabe was offered — this was an analogue computer that calculated time from the positions and that got its name from its similarities to an astrolabe. The practical problems were severe and the method was never used at sea. However, it was used for longitude determination on land.

Quiz Question

One of a continuing series

Technology-Charger-02

When I was out in California a few years back there was this public service ad that kept popping up on cable TV. It featured three teens having a conversation. One little girl was being chided by her friends for leaving her phone charger plugged in when she wasn’t actually charging her phone. That sounded cool. Don’t waste electricity needlessly. Of course, not much goes into powering a smart phone charger, so it’s not like leaving the A/C turned on when you go on vacation.

Then it occurred to me that phone chargers don’t draw power when they aren’t charging the phone. And that’s this week’s Quiz Question. What’s a quick and painless way to verify your phone charger is not drawing power when it’s not charging?

Post your answer in the comments section.

Update and answer

Mike has the right idea (see the comments), but it is not as hard as he makes out. Just put your hand on your phone charger. If it’s warm, it’s dissipating (and wasting) power. You don’t need a sensitive thermometer. With most devices I’m thinking you can feel the temperature rise due to one Watt, or less.

Quiz Question

One of a continuing series

TechnologyWallSwitch

When you want to turn on the stair lights while going up the stairs, and you want to turn them off once you get to the top, you need this bit of minor technology. The lights are controlled by two switches. One switch is at the bottom of the stairs, and the other switch is at the top. The switches are “double throw” type. That means the switch is connected to two circuits, and the switch has two positions. When you toggle the switch it turns off one circuit and turns on the other. If the light was on, then throwing the switch turns the light off. If the light was off, then throwing the switch turns the light on. Neat.

Now suppose you have a three-story house, and you want to turn the stair lights on when starting up, and you want to turn the lights off when you get to the second floor, and also off when you get to the third floor if you are going that far. How are you going to be able to achieve that? Do you need a new kind of switch?

What if you have a 15-story house?

Post your answer in the comments below.

Update

Some comments have been received, and it’s apparent clarification is needed. This Quiz Question involves single-pole, double-throw switches. Here is how a SPDT switch works:

SPDTSwitch

Update and Solution

The two-switch feature can be extended to more than two switches, but the configuration I had in mind does not work. I had to go to Wikipedia for a workable solution. First, here is how the two-switch configuration works.

 

Technology-DoubleThrow-03

Technology-DoubleThrow-04

Switch 1 and Switch 2 are SPDT switches. In the first configuration no power is supplied to the load, which is typically a lamp. In the second configuration power is supplied to the lamp, and it turns on.

It is trivial to extrapolate from this and determine that flipping either switch turns on an off-lamp and turns off an on-lamp.

To extend this idea to more than two switch requires a different kind of switch, but still a mechanical switch. The following are from Wikipedia:

Readers are invited to visit the Wikipedia article, following which they will be able to install multi-way lighting switches for their five-story condo.

Quiz Question

One of a continuing series

Technology-ShotgunShells-01

Steve and Greg, hold off answering this week’s Quiz Question until some others have had a crack at it.

When you go into Home Depot and purchase some electrical wire, you will notice it comes in different sizes. Wire diameter is specified by its gauge. The deal is the smaller the gauge the thicker the wire. You may not also know that a similar gauge system is used for sheet metal. 8 gauge sheet is getting toward boiler plate thickness. 32 gauge is some thin stuff.

When it comes to shotguns, a gauge system is used to specify the bore. The very common 410 shotgun is not a gauge measure. I could be wrong, but I think a 410 has a 0.410-inch bore. The only common shotgun gauges I know are 10-gauge and 12-gauge. Doesn’t matter.

This week’s Quiz Question is, how is a shotgun gauge determined?

Provide your answer in the comments section below. No need to post your answer on Facebook. I always do that when I post the answers.

Quiz Question

One of a continuing series

Airliner crosses Vineland Avenue North Hollywood while landing at Burbank Airport

Airliner crosses Vineland Avenue North Hollywood while landing at Burbank Airport

This is a different Quiz Question. It’s possible the answer will never be known. What you need to do is to do some research. Once you have decided on your best answer, post it as a comment and state your defense of your answer. Here it is:

On 17 December 1903 nobody had ever made a flight in a powered, heavier-than-air craft. There were no airplanes in the air. Then Orville Wright flew for 12 seconds, and then he landed, and again there were no airplanes in the air.

On an unknown day a few years later there were no airplanes in the air. Then somebody took off in an airplane, flew it, and landed. But before the airplane landed, somebody else took off in another airplane. Since that time there has always been an airplane in the air.

The Quiz Question is when was the last time there was not an airplane in the air? I am counting only powered aircraft piloted by a person. Post your answer as a comment below. I will select the winner. The best answer wins Donald Trump’s $50 million prize, to be awarded his second day in office as President.

Quiz Question

One of a continuing series

GPS.gov

GPS.gov

Last week’s Quiz Question concerned GPS (Global Positioning System). A major issue with GPS is the variable caused by ionospheric propagation delay. Free electrons in the ionosphere slow down the signal from the satellite to the receiver, and this effect varies from day to day and with location about the Earth. Since operation of GPS relies on knowing how long (within a nanosecond) it takes the radio signal to reach the receiver, it’s critical to compensate for the ionospheric delay.

Receivers able to receive the L2 (encrypted) channel can compensate for the ionospheric delay as described in last week’s Quiz Question. Without accurate compensation the position error can be off in the order of 15 meters. When the ionospheric delay is properly compensated, the error can be reduced to the order of a few inches.

GPS has been available to the public for over 20 years, and people like farmers use GPS navigation to plow their fields. Without decoding the L2 signal they can they compute the location of their tractors to a few inches? This is done with the use of Differential GPS (DGPS), and it works this way.

Set up a GPS receiver at a known point. Use another receiver on the tractor to navigate with a few inches accuracy. Neither receiver is able to decode the L2 signal. How does DGPS accomplish this accuracy?

Post your answer as a comment below.

Update and solution

Without researching into how DGPS is implemented, I will explain a possible method. The location of the reference receiver is known. This allows it to compute the ionospheric delay. Since the other GPS receivers (for example, on the farmer’s tractor) are nearby, the ionospheric delay is the same for them. If the active GPS receivers can receive the ionospheric delay from the reference receiver, they can compensate for it and obtain their location within a few inches.

The compensation for ionospheric delay is detailed in the GPS Interface Control Document, publicly available on the Internet. Here is the link:

http://www.gps.gov/technical/icwg/ICD-GPS-200C.pdf

Quiz Question

One of a continuing series

GarminGPSIII

Here’s something that came up a few years ago. It has to do with GPS technology, but you don’t need to be GPS-savvy to appreciate it. It goes like this.

GPS employs 32 satellites, whose position is at all times precisely known. Each satellite broadcasts to Earth continuously. The signal contains a lot of stuff, but the critical information from each satellite is:

  • I am here.
  • The time is …

A GPS navigation receiver doesn’t need to know the direction the signal is coming from. All that is necessary to determine your position is the preceding information from each of three or four (four is best) satellites.

From the information received, a navigator can determine where all satellites were at the same time. And it can determine how long it took each satellite’s signal to reach the receiver. Knowing the speed of propagation of the radio signal, the receiver can compute the distance to each of three (or four) known points in space and therefore compute its own position in 3-D space. If it knows the speed of propagation of the radio signal.

The problem is the speed of propagation through the atmosphere to the receiver is not constant. It varies due to the presence of free electrons in the atmosphere. There are two solutions to this difficulty. One is to incorporate an atmospheric model into the receiver’s computation, and this is done. It’s called the Klobuchar model, after the person who developed the mode. It’s not very accurate.

For extreme accuracy, the atmospheric delay can be measured directly. To do this, a second transmission channel is incorporated.

The two satellite transmission channels are called L1 and L2. All receivers can use L1. L2 is encrypted. You have to have a secret key, available only to the U.S. government, to use the L2 channel. The two channels operate on somewhat different frequencies, and the atmosphere delays each channel differently.

And that’s all you need to know if you can receive both L1 and L2. You do not need to know in advance how the atmosphere delays each channel. The receiver can deduce the atmospheric delay from each satellite, and from that it can compute the position of the receiver to very high degree of accuracy.

When I first encountered this it was obvious to me there was not enough information to compute the atmospheric delay. So I asked a guy working on the project how this was supposed to work, and he stopped what he was doing and explained it to me. I still didn’t understand it, but I took my notes back to my cube and looked at it some more. It was an “oh shit” moment. “Of course, dummy.”

And that’s this week’s quiz question. How can a GPS receiver compute the atmospheric delay from the information given, using L1 and L2?

Post your answer as a comment below. I’m going to give this a few days and then post a hint.

Update and hint

I’ve had no activity on this Quiz Question all week. It’s time to provide a hint. Look at the problem again.

You have two radio signals originating from the same location at the same time and arriving at the receiver at different times. Because of ionospheric delay, you don’t know how long it took either signal to traverse the unknown distance to the transmitter. How can you use the information available to determine the distance to the transmitter. Here is the hint.

The satellite is moving. In the order of miles per second. Its distance from the receiver changes from one transmission to the next. How can you use multiple measurements to compensate for the ionospheric delay?

Update and solution

Time’s up. I need to post the solution to last week’s Quiz Question, because tomorrow’s question is going to be related to compensating for ionospheric delay. I’m not going to do the math. Instead, I’m going to pose the question in a different way that will make the solution obvious. It goes like this:

Forget satellites. There are two rail lines running parallel for miles over the horizon. You’re standing at a point along the rail lines waiting for two trains (call them A and B) to arrive. The two trains are going to start at the same time from the same location, and they are going to come at you at different speeds. You don’t know what the speeds are, but you know the speeds of A and B are different, and they are constant.

Trains A and B arrive. A arrives shortly before B. You note the time difference. You don’t have enough information to determine how far away the station (starting point) is. You move down the line a few miles, carefully noting how far you move.

Two more trains, also labeled A and B head your way from the station. Same as before. A arrives, then B arrives later. You record the time difference. Of course the difference is greater, because you are farther from the station, so the trains have had longer to diverge.

Now you ask yourself this question. “How far do I have to walk toward the direction the trains came from for the difference to be zero?” That’s the distance to the station.

In the case of GPS with channels L1 and L2 it’s the satellite that moves, and since the satellite is always telling you where it is, you know how much farther (or closer) it has moved from you between two measurements.

There is obviously more to it, so if anybody still has questions, post a comment and extend the dialogue.

Security Mania

Home security has been a hobby of mine since I retired. Allow me to refer you to a previous post. An item I found particularly useful was this:

I was much impressed with the concept and decided to expand my system, but on the cheap. A more affordable option is the CDS-930L that doesn’t have tilt and rotate control, lacks some of the other features, and has less image quality. At $30 each from Amazon (free shipping and no sales tax), these are a real bargain.

DCS-930L-01-512

As mentioned, I have two of these, and may add more. When I enable the feature each one sends an email to me when it detects motion—such as when a burglar walks into the field of view. The email carries six attachments: three images captured just prior to detecting motion plus the follow three. See the previous link.

Another feature is FTP capability. FTP is the Internet File Transfer Protocol, and it works like this. If a computer on the Internet is running an FTP server, and the computer receives a datagram designating port 21, then the FTP server is activated and handles the message. The message will initiate a dialog between the computer and the sender. The dialog will likely comprise one or more of the following:

  • Host computer requests a user ID.
  • Host computer requests a password.
  • Host computer verifies the user ID and the password, and continues the dialog.
  • Host computer executes any number of FTP commands from the sender—receive a file, save the file in a directory specified by the sender, delete a file, transmit a file from the host to the sender. And so on.

Computer guys already know this stuff.

Besides the ability to send images by email, the CDS-930L can send a stream of images to a specified FTP server, as often as one each second. Since the CDS-930L doesn’t have file storage, this is the only way to capture an image stream with one of these. A problem is, you need an FTP server somewhere on the Internet. One way I suppose you can get access to one is to subscribe to a cloud storage service, but that costs money, and I was looking for a way to do this on the cheap.

Cheap is a relative term, and for me this translated into a computer I have sitting on the shelf not doing anything. Many months ago I purchased a refurbished Dell Latitude E6400, and then I drove to Best Buy and obtained a 1 TB drive for it. I installed the new drive and then installed Ubuntu Linux on it. And that brings up the tech exercise of today—how to set up an FTP server on Ubuntu Linux.

I wisely elected not to build my own server, which would be possible. I have had for 20 years the excellent book by W. Richard Stevens (now deceased) titled UNIX Network Programming. The book explains how to construct all manner of network software, and there’s more. The code is available on the Internet. You don’t have to write it. Just copy, modify, compile.

Talk about cheap. There’s an even cheaper way. Ubuntu Linux (and other flavors, besides) comes with an FTP server. All you have to do is to activate it, and you’re on-line. Not being a Ubuntu professional, what I did was go to the Internet for help. Particularly, I went to a page on Krizna.com. Here are the instructions, modified by me:

How to setup FTP server on ubuntu 14.04 ( VSFTPD )

There are 3 popular FTP server packages available PureFTPD, VsFTPD and ProFTPD. Here I’ve used VsFTPD which is lightweight and less Vulnerability.

Step 1 » Update repositories .
$ sudo apt-get update

You execute the apt-get update command, preceded by “sudo,” or super user do. This executes the command as though you were a super user, which you must be to do this kind of stuff on Linux (or UNIX).

Step 2 » Install VsFTPD package using the below command.
$ sudo apt-get install vsftpd

You only need to do this if your installation of Ubuntu does not already have vsftpd. It turned out mine already had it, and when I attempted to install it I was told it was already installed, and nothing was done in response to the command. You can check to see whether you already have vstfpd by checking the /etc directory. See the following.

Step 3 » After installation open /etc/vsftpd.conf file and make changes as follows.
Uncomment the below lines (line no:29 and 33).
write_enable=YES
local_umask=022
» Uncomment the below line (line no: 120 ) to prevent access to the other folders outside the Home directory.
chroot_local_user=YESand add the following line at the end.
allow_writeable_chroot=YES» Add the following lines to enable passive mode.
pasv_enable=Yes
pasv_min_port=40000
pasv_max_port=40100

Step 4 » Restart vsftpd service using the below command.
$ sudo service vsftpd restart

There are some additional steps. See the Krizna page to see more. I did not need to do any of this, as explained below.

I next had to open up my Linksys router to determine the IP address of my E6400. It turned out to be 192.162.1.101, an address that needs to remain stable if this whole business is going to work. I pulled up a DOS window on my Dell Studio 17 and initiated the following dialogue:

$ ftp 192.168.1.101
Connected to 192.168.1.101.
220 (vsFTPd 3.0.2)
User (192.168.1.101:(none)): john
331 Please specify the password.
Password:
230 Login successful.
ftp>

See, my E6400 was already set up with a user name and password, and that’s all FTP needed. I quit out of that, because this was only to confirm the FTP server was running and that I could access it. The next task was to set up a CDS-930L to send images by FTP.

I know the IP addresses of my two CDS-930Ls, and I entered one in a browser window to get to the camera’s control panel:

Technology-DCS-930LB-FTPPane

Here I have:

  • Set the host address to 191.168.1.101
  • Set the port number to 21
  • Entered my user ID (john)
  • Entered my password for the E6400
  • Specified the images from this camera are to go to the /TVRoom sub directory
  • Set passive mode
  • Selected Always so it will run forever
  • Specified one frame every two seconds
  • Selected Date/Time Suffix so no images will be overwritten
  • Told it to create a new sub folder for every hour.
  • Checked the box to enable this operation
  • Clicked the Save Setting button to get the operation started

There is another button below you can click to test operation. It will send a text message to the FTP server, and you can go to the server to see if the message arrived, or you can go to the camera STATUS pane to see if the FTP test passed.

Setting up the FTP server requires editing the configuration file, as shown above. You will need super user privilege to do this. What I did was use super user privilege to allow anybody (me) to change the file. I used the vi editor to edit the configuration file. If you are not familiar with vi, then you will need to use a friendly text editor on your Linux box. Note the following two lines added to the configuration file:

pasv_min_port=40000
pasv_max_port=40100

This specifies the range of ports the FTP server will use. Allowing 101 ports will allow as many as 101 connections at a time. I am only using one for each camera, plus one for remote management of the image database from my Dell Studio system.

To show what can be done, here is a dialog to retrieve an image from the database. The commands were executed from my Dell Studio:

user@Laptop64 /cygdrive/c/DVD/D-Link/images
$ ftp 192.168.1.101
Connected to 192.168.1.101.
220 (vsFTPd 3.0.2)
User (192.168.1.101:(none)): john
331 Please specify the password.
Password:
230 Login successful.
ftp> cd TVRoom
250 Directory successfully changed.
ftp> dir
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
drwxr-xr-x 20 1000 1000 4096 Apr 15 23:59 20160415
drwxr-xr-x 12 1000 1000 4096 Apr 16 10:00 20160416
226 Directory send OK.
ftp: 132 bytes received in 0.00Seconds 132.00Kbytes/sec.
ftp> cd 20160416
250 Directory successfully changed.
ftp> dir
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
drwxr-xr-x 2 1000 1000 114688 Apr 16 01:59 0000
drwxr-xr-x 2 1000 1000 110592 Apr 16 02:59 0100
drwxr-xr-x 2 1000 1000 110592 Apr 16 03:59 0200
drwxr-xr-x 2 1000 1000 118784 Apr 16 04:59 0300
drwxr-xr-x 2 1000 1000 122880 Apr 16 05:59 0400
drwxr-xr-x 2 1000 1000 110592 Apr 16 06:59 0500
drwxr-xr-x 2 1000 1000 110592 Apr 16 07:59 0600
drwxr-xr-x 2 1000 1000 118784 Apr 16 08:59 0700
drwxr-xr-x 2 1000 1000 110592 Apr 16 09:59 0800
drwxr-xr-x 2 1000 1000 69632 Apr 16 10:32 0900
226 Directory send OK.
ftp: 620 bytes received in 0.00Seconds 620.00Kbytes/sec.
ftp> cd 0900
250 Directory successfully changed.
ftp> dir
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
-rw-r–r– 1 1000 1000 30663 Apr 16 10:00 DCS-930LB2016041609000101.jpg

I logged on and navigated down to the TV room directory. I listed the directory contents and saw that since I set thing up yesterday the CDS-930L had created two new sub directories, one for 15 April and one for 16 April, as instructed through the FTP setup page above. I next navigated down to today’s subdirectory and had a look around. Sub directories had been created for hours 0 through 0900. Good. Everything is running as hoped for. I navigated to the 0900 page and listed the images. And it listed several pages of images. I’m only showing one. FTP finished up and said it was through sending the directory.

226 Directory send OK.
ftp: 85956 bytes received in 0.15Seconds 569.25Kbytes/sec.
ftp>
ftp> bin
200 Switching to Binary mode.
ftp> get DCS-930LB2016041609000101.jpg
200 PORT command successful. Consider using PASV.
150 Opening BINARY mode data connection for DCS-930LB2016041609000101.jpg (30663 bytes).
226 Transfer complete.
ftp: 30663 bytes received in 0.09Seconds 356.55Kbytes/sec.
ftp> quit
221 Goodbye.

As you can see, I ensured the FTP was in binary mode, because images are not text files. Then I commanded get (an image). And here is the image. It’s deadly dull. My TV room on a dark and stormy Saturday morning. Nothing to see here, folks. Keep on moving.

DCS-930LB2016041609000101

With a TByte drive I figure I can go on vacation for a month or more and collect an image every two seconds from each of two cameras and have room to spare. If I get notification from one of the cameras that somebody is prowling around my house I can, when I get home, get all the appropriate images from the computer drive and take them down to the police station. Provided nobody steals the computer. And that’s the deal. The computer needs to be in an inconspicuous place so it will still be there.

This only covers security against burglary. The setup can be used for other purposes. In our neighborhood we have a single street leading in and out. We have a sign at the entrance announcing video surveillance is operating. The problem is, we don’t actually have any video surveillance. This would be a cheap way to implement neighborhood surveillance. Just point a camera out a window and let it run all the time. Something bad happens, and the police need to be called, we check the video record to see who was driving on the streets.

Feedback is welcome. Add a comment or send me an email.

The Undecidability Problem

AlanTuringTheEnigma

I’m confident that nobody who has gone through a computer science degree program is unaware of the undecidability problem and the Turing Machine. Some excerpts from the Wikipedia entry sum up the matter:

In computability theory and computational complexity theory, an undecidable problem is a decision problem for which it is known to be impossible to construct a single algorithm that always leads to a correct yes-or-no answer.

and

In computability theory, the halting problem is a decision problem which can be stated as follows:

Given the description of an arbitrary program and a finite input, decide whether the program finishes running or will run forever.

Alan Turing proved in 1936 that a general algorithm running on a Turing machine that solves the halting problem for all possible program-input pairs necessarily cannot exist. Hence, the halting problem is undecidable for Turing machines.

In full disclosure, I took the course and made an A, but the matter is still hazy to me, and it’s not something I have lost a lot of sleep over. What did interest me was Alan Turing’s work in cracking the Enigma code used by the Germans in World War Two, and that was my reason for obtaining the motion picture about these events, The Imitation Game. A review will be posted on the fourth of May, but in the meantime I obtained a copy of the book that formed the basis for the movie. It’s Alan Turing: The Enigma, and it’s more about Turing and less about the German Enigma. The image above is from the Kindle edition of the book, and it appears to have been taken from the movie. The book also has a photo of an Enigma.

EnigmaOpen

The naval Enigma machine with its lid raised to show the four rotors. Hodges, Andrew (2014-11-10). Alan Turing: The Enigma: The Book That Inspired the Film “The Imitation Game” (p. ix). Princeton University Press. Kindle Edition.

Andrew Hodges has delivered a masterful, some might say exhaustive, volume on the life and works of British mathematician Alan Turing. The book came out in 1983 after two years of presumably solid writing. I will only touch on some high points.

With his description of what is now called the Turing Machine, Alan Turning is often pointed out as the father, or else the godfather, of the modern computer industry. Others before and after made huge contributions. Charles Babbage, another Englishman, laid out the concept of a mechanical device that is the true forerunner of what we now call a computer, and Ada Lovelace, daughter of English poet George Lord Byron and also assistant to Babbage, is considered to be the first computer programmer. A computer programming language (Ada) is named after her. Arguably the first working computer is attributed to John Vincent Atanasoff, although the Atanasoff-Berry Computer was not programmable. Turing’s concept of a programmable computer is given credit for cracking the code of the German Enigma.

Turing’s early life does not give the picture of somebody about to break thresholds in mathematics and signal counterintelligence. As a child he was an uninspired student who at a point in his academic spiral showed a gift for mathematics. This earned him a place at Cambridge King’s College, and Hodges gives his American readers a guided tour of the British system of matriculation, another matter I have yet to comprehend.

A central part of the book is how Alan Turing’s interest in a peculiar field of mathematics set him onto a course to take on the German war machine. I’m familiar with some of the background, but I’m going to take care not to bore you with a lot of depth. Suffice it to say that in the early 20th century there were items of interest being fiercely pursed in one small corner.

In 1900 German mathematician David Hilbert set forth a number of mathematical issues that needed to be resolved. One statement of his was

that every definite mathematical problem must necessarily be susceptible of an exact settlement …

[Hodges, Andrew (2014-11-10). Alan Turing: The Enigma: The Book That Inspired the Film “The Imitation Game” (p. 118). Princeton University Press. Kindle Edition.]

In Vienna in 1931 Kurt Gödel

demonstrated that any non-contradictory formal system, which was comprehensive enough to include at least arithmetic, cannot demonstrate its completeness by way of its own axioms

thereby refuting Hilbert’s assertion. What Alan Turing did was to use his concept of a computing machine as a means for computing all possibilities of  “computable numbers.” He demonstrated the Turing Machine could not compute all numbers, therefore there must be a solution to some problem statement that could not be computed.

The major theme of this book is how the Turing Machine concept led to the cracking of the Enigma code. The German Enigma was not a secret machine. Prior to the war commercial copies had been sold and used by businesses wishing to keep their correspondence private. Particularly, the German Navy used a modified version. Enigma worked by translating a character entered from the keyboard into a different character, displayed by a lighted position in an array of letters. Additionally, every time a key was depressed, a set of rotors would advance and produce a different connection between the keyboard and the display. The German Navy upgraded the operation of their Enigma devices throughout the war by adding more rotors and patch-plug connections.

Prior to the war the British became concerned about being able to read German signal traffic in the event of hostilities, and they worked with the Poles, who had obtained a purloined copy of a military Enigma and had developed a way to crack the code. Bare days before the Germans invaded Poland the Polish copy and accompanying cryptanalysis technology were spirited out and into British hands.

The movie shows Alan Turing being interviewed for a position on the cryptanalysis team by Commander Alastair Denniston, director of the British Government Code and Cypher School (GC and CS). Denniston was a real character, but the interview is a fake. Turing began working with GC and CS prior to the war and never was a reluctant candidate. Neither was he the abrasive co-worker who deigned to work with others as depicted in the movie.

The connection between the Turing Machine, none of which was ever constructed, and the cracking of the Enigma is that the concept of the Turing Machine is an automaton that can be adapted to perform a multiplicity of tasks by modifying its collection of control states. The concept of a collection of states has since morphed into what we now call a computer program, and it was the idea of constructing a machine controlled by a variable program that enabled the defeat of Enigma.

The team at Bletchley Park, where the British carried out cryptanalysis during the war, was able to crack Enigma codes by feeding message intercepts into an automaton devised by Turing and trying different rotor settings until the output contained legible verbiage. What assisted them throughout the war was incompetence on the part of the German operators. The careless inclusion of expected words allowed the code breakers to vastly narrow their search. Turing’s variable control set allowed adapting the search without reconstructing the machine whenever the Germans made a change in their Enigma.

A parallel theme that runs throughout the book is Turing’s homosexuality. As a boy he realized he found male bodies more attractive than females, and the book is a life-long tale of Turing dealing with his homosexuality. In England at the time homosexual acts were criminal, but nothing came from Turing’s homosexual lifestyle until years after the war, even though he never went to lengths to hide his orientation. Remarkably, Turing was throughout his life almost fatally honest, and he was casual in disclosing his homosexuality to co-workers and friends.

Someone watching the movie may get the idea that Turing’s arrest in 1952 (the movie has it 1951) for “gross indecency” with a male lover was his downfall. This was not the case. Turing admitted all details once the facts were reported to the police, and he and his partner entered guilty pleas at their trials. Turing did not lose his job at the University of Manchester. He served a one-year probationary sentence, which required he receive estrogen treatments to effect chemical castration. He continued to pursue his new interests in scientific research up until 7 June 1954, when he apparently dipped an apple in cyanide solution and bit into it. He left no suicide note.

Hodges introduces the term “imitation game,” the title of the movie. It has a double meaning. On the one it’s the science of cryptology, the masking of messages. On the other it’s Turing living and working as a homosexual in plain sight within a society that criminalizes his lifestyle.

Hodges takes what could otherwise be a great spy thriller and turns it into an English prose tour de force. His analysis in depth is little matched by the likes of Gustave Flaubert and D.H. Lawrence. For example:

He had clung to the simple amidst the distracting and frightening complexity of the world. Yet he was not a narrow man. Mrs Turing was right in saying, as she did, that he died while working on a dangerous experiment. It was the experiment called life – a subject largely inducing as much fear and embarrassment for the official scientific world as for her. He had not only thought freely, as best he could, but had eaten of two forbidden fruits, those of the world and of the flesh. They violently disagreed with each other, and in that disagreement lay the final unsolvable problem. In this sense his life belied his work, for it could not be contained by the discrete-state machine. At every stage his life raised questions about the connection (or lack of it) between the mind and the body, thought and action, intelligence and operations, science and society, the individual and history. But these were questions on which, except in the most special ways, he went out without a word of comment. Russell and Forster, Shaw and Wiener and Blackett held forth on such subjects; Alan Turing played the humble pawn.

Hodges, Andrew (2014-11-10). Alan Turing: The Enigma: The Book That Inspired the Film “The Imitation Game” (p. 659). Princeton University Press. Kindle Edition.

That, in combination with stringent attention to detail, runs to 663 pages of narrative. Following are 63 more pages of notes and index. It’s a lot to digest, and the casual reader will at times wish for a Cliff’s Notes. As a research into the life and works for Alan Turing it may be unmatched.

Quiz Question

One of a continuing series

All tech geeks know the answer to this one, but here it is. What is the relationship between the two images?

Winchester Hard Drive

Hard Drive

Winchester73-01

Don’t post your answer on Facebook. Use the comments section below.

Update and answer

Michael has provided the correct answer. See the comments section below. The computer hard drive and the rifle in the photo are materially related. The rifle is a Winchester 73, from the movie of the same name. The computer disk drive technology was developed by IBM corporation and named after the rifle:

In 1973, IBM introduced the IBM 3340 “Winchester” disk drive, the first significant commercial use of low mass and low load heads with lubricated platters. This technology and its derivatives remained the standard through 2011. Project head Kenneth Haughton named it after the Winchester 30-30 rifle because it was planned to have two 30 MB spindles; however, the actual product shipped with two spindles for data modules of either 35 MB or 70 MB.[11] The name ‘Winchester’ and some derivatives are still common in some non-English speaking countries to generally refer to any hard disks (e.g. Hungary, Russia).

Hopefully Michael answered the Quiz Question from memory, which is one of the expectations of the game. My own memory was that the name was derived from Winchester Blvd. in San Jose, CA, where the IBM development office was located. This has turned out to be an urban legend:

It was my (admittedly undocumented) impression that the Winchester Disk was named not for the Winchester Rifle, but for the location of the IBM office on Winchester Blvd in San Jose. Perhaps this is an urban legend but I recall hearing it many years ago. Jim Bowery 23:35, 19 September 2006 (UTC)

Added IBM source to article. 30-30 must be a Winchester [rifle] tooold (talk) 06:35, 21 January 2009 (UTC)
The folklore I’ve heard is that the technology was named Winchester after the rifle, because the team was working on dual 30 MB drives (30+30 MB), hence the “30-30” connection with the rifle. —Loadmaster (talk) 01:09, 22 March 2013 (UTC)

Ken Haughton code named it Winchester for the rifle because the program was initially two thirty MB spindles in a box, called “30 – 30” by some. See his oral history, p.9. Tom94022 (talk) 05:32, 22 March 2013 (UTC)

The folklore about Winchester road name was widespread in the years I worked at the San Jose plant. This may be a case where a name was suggested and multiple reasons were found to sustain it.HiTechHiTouch(talk) 01:27, 3 March 2016 (UTC)

Note that these two lines of folklore are connected. Winchester Blvd was named for Winchester House, which was built by Sarah Winchester, who inherited 50% of the Winchester Repeating Arms Company, inventor of the .30-30 Winchester center fire cartridge. 02:58, 3 March 2016 (UTC)

The source of the urban legend about the boulevard is not known, but it is clear from Haughton that the name came from the rifle. Given the bredth of the urban legend it might be worth an in-line note in the article debunking it. Tom94022 (talk) 18:37, 3 March 2016 (UTC)

A small technical issue: The rifle in the movie is a .44-40, not a 30-30. Readers would know this if they watched the movie. At the trading post we hear outlaw ‘Ditch’ Henry trying to purchase .44-40 ammunition for the Winchester 73 he just stole from his brother (played by James Stewart). Fact is, the Wikipedia entry for the Winchester 73 does not list a 30-30 model. Loan of the DVD on request.

Quiz Question

One of a continuing series

Racers aren’t allowed to answer this one.

The item pictured below is a carburettor jet.

Cycle Pro Pilot Jet for Keihin Carb

Cycle Pro Pilot Jet for Keihin Carb

Before just about everything went to fuel injection, there were carburettors. Carburettors supply a mixture of air and fuel to the intake ports of piston engines. They work this way.

On the intake stroke of an engine, the piston moves down, drawing air into the cylinder. Air flows rapidly into the cylinder, passing first through the carburettor. The air stream through the carburettor, because of its forward motion, exerts reduced pressure against the side walls of the port. The carburettor jet connects the air stream to a supply of fuel in a float bowl, a small reservoir of fuel in the carburettor body. The reduced pressure causes fuel in the float bowl to be forced through the opening in the jet and into the air stream. The fuel mixes as a spray with the air stream and is carried into the combustion chamber.

The carburettor jet has a measured opening for the fuel. A larger opening will allow more fuel to flow into the air stream. Here’s the question. A motorcycle racer (for example) arriving at the track in the morning observes it’s a warm and humid day. He opens up his race kit box and selects a set of jets with larger openings and installs them in all the carburettors in his engine.

Why? Why does the racer know he’s going to need a larger jet?

Provide your answer as a comment below. If nobody provides the correct answer by Friday I will post it here.

Update

The answer to the Quiz Question is that warm air and moist are are less dense. The equation shows the relationship between pressure (p) and density (ρ) for incompressible flow. I’m using this, since no compression or expansion of the air takes place inside the carburettor throat.

BernoulliEquation

The velocity of the airflow is v. The remaining terms are g and z, the acceleration of gravity and the altitude, neither of which figure into the carburettor operation, all other things being equal. For a given velocity, p and ρ must be proportional. If ρ goes down, p must go down. When the air is less dense the pressure must go down. You need a larger opening in the jet to allow the proper amount of fuel into the air stream, else the cylinder will burn too lean. The result would be a burned piston.

Stand by for another Quiz Question on Monday. And keep reading.

Quiz Question

Forty-five years ago I worked for an engineering consulting company. We did design and development for companies that did not have their own engineers.

This was at the dawn of self-service gas stations, and new companies were getting into the business. One had a chain of stations called Fill-Em-Fast. It was Autotronics out of Houston. What they wanted was to get sales information on a daily basis. This was before the days of the Internet and instant sales reports. What they wanted us to do was to electronically record sales information, gallons and dollars, from each pump. At night, when phone rates were low, the home office would phone each station in turn and retrieve the sales information from the station’s box. We designed that.

This Quiz Question regards a problem involving the retrieval of sales information from pumps. These were the mechanical pumps of your grandfather’s day. There was a mechanical display operated by gears as the fuel was dispensed. We figured all we needed to do was to hook into the rotation of the gear shafts and read the revolutions, or increments of same. That’s where the following image comes in.

gear

We would fit an extra spur gear on the shaft we wanted to read off and just count the gear teeth as they went by. Don Ninke was the EE in charge of this, and he came up with a design that counted teeth with an optical interrupter. An LED would send out light, and a photo-diode would receive it. Gear teeth would interrupt the beam, and we would count the pulses.

It didn’t work. It counted too many teeth. And that’s the Quiz Question. Why didn’t this work? Why was this design counting too many teeth?

Part two of the Quiz Question: How did Don fix the problem and count the correct number of teeth?

As always, post your answers in the comment box below. I will provide the answer Saturday, or before.

Solution

Mike has provided the answer:

Backlash. If you have two sensors, you can tell the direction of motion.
Used this technique on the automobile odometer cable for a time-speed-distance car rally computer.

Mike obviously has had some engineering experience. This is the solution Don Ninke came up with. The applicable term is “quadrature.” Set the two sensors out of phase by 90°. If the gear backs up a tooth, one is subtracted from the count. See the diagram.

Quadrature

Quadrature

 

Counter rotation of the gear shaft typically occurs when the mechanism stops. There’s not much problem when the pump is running, and the shaft is turning continuously. Discounting spurious pulses has two benefits:

  • You don’t over charge the customer for an extra tooth’s worth of gas.
  • At the end of the day you don’t have have the accumulated error of these extra counts, which would screw up the accounting. There were separate shafts for the dispensed gas and dollars charged. They really need to match at the end of the day.

Interesting thing to note: The only computer used in the system was a Data General Nova 1200 mini-computer. That was installed in the home office in Houston, and Wayne van Citters and I did the software for the Nova.

The electronic box that Don Ninke designed employed no processors. It was all series 7400 logic chips from Texas Instruments. It counted pulses and recorded sales from the pumps, accepted calls over a phone line, and spewed out the sales data for the day over an RS-232 link.

About this time (early 1972) we learned there was a company developing a computer on a chip. We requested and obtained a spec sheet dated late 1971 from Intel. I still have it—two Xeroxed sheets on the 8008 microprocessor. It was an amazing time.

Quiz Question

One of a continuing series

See the diagram below.

For about eight years I worked for a company that made document processing systems. One of the company’s inventions was a high-capacity ink jet printer. It worked as shown.

InkJetPrinter

There was a nozzle that spit out 105,000 ink drops per second. A variable voltage was applied to the nozzle, which charge was retained by each ink drop as it exited the nozzle. The voltage was changed for each drop.

The drops passed between two charged plates. Drops with differing charges were deflected in different directions by an amount proportional to their charge. It was a touchy situation. The voltage needed to be something like 5000 volts between the two plates. Not enough voltage, and the drops would not be deflected enough. Too much voltage, and electricity would arc between the plates. I spent weeks getting a configuration that would work. Ink drops were properly deflected, and there was no arcing.

We installed our systems in major banking and financial centers around the world. Then I asked a question. “Do we have any customers in Denver?”

And the quiz question is this. Why did I ask that question?

Solution

Mike apparently saw the answer right away. I asked him to hold off before posting his comment. And here it is.

From high school physics we know that dry air breaks down at 25,000 Volts per inch. That’s dry air at sea level. When the air gets thinner at higher altitudes it breaks down at lower voltages. This arrangement featured two charged plates operating on the verge of breakdown. That was one of the big problems, as noted in the statement of the problem.

It was obvious when we finally got this thing to working that it wouldn’t take much to tip the balance and induce arcing. An increase of one mile in altitude would surely do it.

As it turns out we didn’t have any systems installed in Denver, La Paz or any other troublesome locations.

Provide your responses in the comments below.

Home Security Revisited

Home security is not my foremost interest, but it’s up there among the things that get my attention. My new (2010) house in San Antonio has the standard security system, one that detects and sounds an alarm when somebody opens a door or a window. I got really interested last year when an unknown person started to barge in the front door at 3 a.m. while Barbara Jean was in the living room knitting. I already had some additional home security features, but that got me to experimenting some more. Here are some findings.

Z-Wave

By that time last year I already had dipped into Z-Wave technology. Z-Wave is an industry standard, and a number of manufacturers produce systems and components. Any component conforming to the standard can be inserted into an existing Z-Wave network.

I went the cheap route. I purchased a VeraLite controller by Mi Casa Verde. It’s now about $103 on Amazon, but two years ago I paid more. Things are getting cheaper. There is a full-blown Vera controller that has more capability and costs more if you want to go that way. The controller hooks up to your home computer network. It doesn’t have WiFi. You have to cable it to your router. The controller communicates with various Z-Wave devices throughout your home by means of its own radio network. The devices and the controller keep in constant communication with each other.

VeraLiteController

VeraLite Controller

More importantly, in the case VeraLite, the controller communicates with its home office by means of your Internet provider. The manufacturer maintains a central server as a free service to people using its products. With their free app for your smart phone, you can be in Wichita, Kansas, and monitor and control the devices in your home in San Antonio. Here are some of the devices you might want to control.

Wall receptacle

Wall receptacle

Here is a Z-Wave wall receptacle. This one is by General Electric, $36 from Amazon. Replace a standard outlet with this, and you can turn on and off the bottom outlet (not the top one) with the Z-Wave controller. You can also see the status (on or off) on your VeraLite app.

Too late after purchasing and installing a number of these, I discovered a better way of doing it. Replacing the standard duplex outlet with one of these is a real bear. The Z-Wave controller takes up a lot of room in the box, and you really have to work to crowd it in along with the wiring that’s already there. The better solution is the pluggable appliance module.

LampModule

Plug this into any active wall outlet, and you have a ready Z-Wave outlet. This will consume one receptacle of a duplex outlet, leaving barely enough room to plug in another lamp or appliance. The good news is the appliance module has two outlets, one controlled and the other just a pass through from the wall outlet. This one is from General Electric, currently $35 on Amazon.

Z-Wave power outlets are useful for things you plug into the wall. For ceiling lights and such you need to replace a standard wall switch with a Z-Wave switch.

Wall switches

Wall switches

Here I have installed two Z-Wave switches into a double switch box. These are also from General Electric at $40 on Amazon. You likely have existing toggle switches installed, but the Z-Wave switch needs to be the rocker type. That’s because the Z-Wave switch only turns power on and off, it cannot move the toggle lever.

The business at my house last year generated much interest in Z-Wave motion sensors.

MotionDetector

These motion sensors are by Ecolink, and they detect motion using passive infra red (PIR) technology. They are currently $30 on Amazon. A good thing about these is they are completely wireless. They have a battery for power, which lasts a number of years before it requires replacing. You can put them anywhere. Mount them on a wall (mounting bracket supplied) or just set one on a table, as shown in the photo.

In a Z-Wave system you use things like motion sensors to activate “scenes.” Scenes in the Z-Wave world are settings for other devices. With the VeraLite controller you can associate multiple delays within a scene. For example, suppose your back door sensor is tripped, and it activates a scene called BackDoor. Associated with that scene could be, for example:

  • Immediately turn on the back porch light and arm the living room motion detector.
  • After 2 seconds turn on the living room light and the upstairs bedroom light.
  • After 1 minute turn on the hall light.
  • After 65 seconds turn off the bedroom light.

The net result will hopefully convince anybody coming to your back door at night that people are home and turning on and off lights, and maybe calling the police. In the mean time the VeraLite controller has sent a message to the company’s server, causing an alert message to be mailed to you. If you are out of town your smart phone will get the email and create a little sound, alerting you to read your email. All of this is, of course, assuming you have set your system up to do it.

And remember, at least with VeraLite, the monitoring service is free. It’s one of the benefits of modern technology. The cost to Mi Casa Verde of setting up a server to do this is next to nothing compared to the income it produces through the sale of its controllers.

Cloud Cameras

Additionally useful are “cloud cameras.” These are video cameras, Webcams if you will, that tie into a cloud server. My brother clued me into some systems provided by D-Link. D-Link makes routers and other stuff, but their cameras will work with any home router system. Here is the first one I got.

DCS-5222LB-01

This is D-Link’s DCS-5222LB, currently $190 on Amazon, but I see it advertised elsewhere for as low as $134. This video camera, as with practically all of D-Link’s cameras, incorporates a WiFi link to your home router. As with VeraLite, the company provides a free monitoring service. Set up an account with the company and register your D-Link product with them, and it will connect to the company server and send alerts. You will receive an email when the company gets the alert.

I was much impressed with the concept and decided to expand my system, but on the cheap. A more affordable option is the CDS-930L that doesn’t have tilt and rotate control, lacks some of the other features, and has less image quality. At $30 each from Amazon (free shipping and no sales tax), these are a real bargain.

DCS-930L-01-512

These cameras have motion detection by means of their imaging system and also by sound detection. When you enable the appropriate alerts, the camera will alert the company server, and you will get an email when motion is detected.

These cameras do more. When triggered by motion or sound they will send images to your email account. This transaction does not involve the company’s server. The camera generates an email message with the images attached, it logs onto your email account using the account information and mail password you have provided and sends the images. The DCS-5222LB additionally will store images and video clips on the flash memory card you insert into the slot provided. Stored images can be retrieved remotely and downloaded to your computer. You can also remotely view live video from your cameras, and when you see something you want to keep you can click on the proper link and retrieve a snapshot immediately. The DCS-5222LB will also save video clips.

A useful feature of both cameras is the transmission by e-mail of a series of six images when triggered by motion detection. To check out this feature I ran a simple test in my house. I pretended I wanted to capture images of an intruder coming from downstairs. I set a Z-Wave motion detector on a small table, along with a DCS-930L camera. I darkened the room by closing the blinds and turning off the lights. I set my Z-Wave system to turn on the lights when the sensor detected motion. Then I dressed myself in a hoodie and dark glasses, because we all know that burglars wear hoodies and dark glasses. Then I came up the stairs. When I entered the darkened room at the top of the stairs the room light came on, and the camera sent the following series of images to me by email.

DCS-930-2015-09-25-01

DCS-930-2015-09-25-02

DCS-930-2015-09-25-03

DCS-930-2015-09-25-04

DCS-930-2015-09-25-05

DCS-930-2015-09-25-06

I didn’t apply PhotoShop to enhance these images. This is how they come from the cheap camera. The first image shows the surprised burglar at the top of the stairs when the lights came on. The next three images show the burglar retreating back down the stairs. The last two images are totally useless, because the burglar is already gone, and all you are getting is images of your stair landing, which you can obtain at any time. I ran similar tests with the DCS-5222LB, which has much better image quality.

I will conclude this introduction to home security and home automation for now. If there is any interest, if there is no interest at all, I will post my experiences with setting up these devices. If you are keen on doing something like this you may want to check back later and step through the tutorials.

Keep reading.

Quiz Question

Base64

This came up when I was working for a company that did secure communications. We were doing the software that formatted the messages and sent them out over the secure link. The messages had to be encrypted prior to transmission. To save communication bandwidth we also wanted to compress the messages.

The question came up: Do we want to encrypt the messages and then compress them, or do we want to compress the messages and then encrypt them. The answer was obvious.

This is a question in two parts:

1. Which should you do first, encrypt or compress?

2. Why?

As with all of these, responses should be posted as a comment to this post. The answer will be provided in slightly more than a week.

Time’s Up!

I have had a couple of responses, and none of them have given the problem any serious thought. I also advised readers to try these concepts out. A small bit of experimentation would have revealed the what, but not maybe the why. And what is the answer?

1. Compress first, then encrypt.

2. You must compress first, because an encrypted file cannot be compressed.

A few minutes ago I ran this simple demonstration. I generated a text file—the first 12 chapters of Genesis. That seemed appropriate.

Next I constructed a simple encryption program, and encrypted the first 12 chapters of Genesis.

Now I had two files—the first 12 chapters of Genesis and the first 12 chapters of Genesis encrypted.

Then I zipped both files. Here is the result:

genesis.txt    39 KB
outfile.txt    39 KB (encrypted Genesis)
genesis.zip    12 KB
outfile.zip    39 KB

The encrypted file will not compress.

People who read the blog would have known this already. This principle was previously explained two years ago:

https://skeptic78240.wordpress.com/2012/08/06/the-codebreakers/

This is the thing that came to me 20 years ago when the question was first posed. It was like, “Yeah, dummy. If you have an encrypted message, and you can compress it, then you are a long way down the road to decoding it.” Since decoding encrypted messages is not usually trivial, compression is out of the question.