[GreenKeys] Re: Ancient Technology

[Don Robert House]

Many thanks for sharing Ben,

We have two examples of the pen register at the museum in San Diego. 
Some of these instruments were used up into the 1950s the newer 
version being the chart recorder.

Regards,
Don



>A nephew of mine is a patent examiner at the US Patent Office in 
>Washington, D.C.  Although he has a BSEE from Washington Univ. in 
>St.Louis, he sometimes asks me questions about old stuff, like 
>batteries and POTS.  Today he asked me what a "pen register" is, and 
>my reply follows.  It covers some technology which makes printing 
>telegraphy look like space age science.=
>
>Ben Stephens=
>
>Return-path: <K9kom@aol.com>
>From: K9kom@aol.com
>Full-name: K9kom
>Message-ID: <122.276b0341.2cceaba8@aol.com>
>Date: Mon, 27 Oct 2003 12:11:04 EST
>Subject: Re: "pen register"
>To: mail@sgain.com
>
>There used to be a gizmo in the old electromechanical telephone 
>offices called a pen register which was used to measure traffic on a 
>telephone trunk.  A roll of paper was slowly drawn under a pen, with 
>the pen tied to the armature of a magnet.  When the circuit was in 
>use, the pen went one way and stayed there for the duration of the 
>call.  When the call ended, the pen went back home and stayed there 
>until the next call.  Later on, a traffic engineer would take the 
>paper roll back to his desk to measure and quantify the marks. 
>These were often multiple units, (like the lie detector of today) so 
>that a whole trunk group could be studied at once. 
>
>Going back before that, there were various attempts to "copy" Morse 
>code by tying a pen to a magnet connected to the circuit, with a 
>roll of paper being drawn under the pen at a uniform speed by a 
>spring driven clockworks.  When the key closed at the other end, the 
>pen was drawn down to make an inked track on the paper ("marking" 
>condition).  When the key opened, a spring lifted the pen from the 
>paper ("spacing" condition).  To this day, the terms "marking" and 
>"spacing" are used in teletype and other data transmission 
>disciplines.
>
>A third use of the pen register was on the McCullough burglar alarm 
>system.  Although predating Morse telegraphy, the McCullough system 
>is cheap and fail safe, and for that reason is still used by many 
>banks, and the insurance companies recognize the McCullough system 
>for lower preferential rates.  It consists of a party line circuit 
>at a DC voltage of anywhere from 48 to 220 volts, with all the 
>stations in a loop.  At the alarm central office there is a pen 
>register which records any and all pulses received by means of a pen 
>on a roll of paper.
>
>Out at the bank, there is an alarm transmitter, consisting of a 
>spring wound clockwork which, when released, will rotate a toothed 
>wheel for one slow revolution.  The toothed wheel drives a contact 
>open and closed, sending pulses unique to that location to the alarm 
>central.  If at the alarm central the attendant sees two marks, 
>followed by three marks, he will look in the code book to determine 
>that location 23 is the First Greedy Bank up at 5th and Main, and 
>will make a phone call to the police with that information.  The 
>advantage of a pen register over a more complicated machine like a 
>stock ticker or teletype machine is its simplicity.  The fewer 
>parts, the more reliable the recorder.
>
>There is a whole lot more to the McCullough system than I can cover 
>in a brief e-mail, but when we visit next, I will go into the 
>details of this alarm system which dates practically to the 
>invention of the DC battery, and is one of the first and still most 
>sophisticated uses of data communication.
>
>And while I'm on to really old stuff, the very first use of 
>electricity was as a burglar alarm.  An alarm company would locate 
>in the central part of the business district, with a battery sending 
>voltage out to a business, with contacts mounted on the door frame. 
>When the door would be forced open, the contacts could close, 
>sending the battery voltage back to the alarm central.
>
>Now to test your brain: This was before the invention of the 
>incandescent lamp or even the buzzer.  How did they indicate to the 
>attendant that the circuit was in an alarm condition?  Well, each 
>customer had a jar of electrolyte on a shelf with the customer's 
>name on it.  The return wire from each customer went to its jar, 
>which included a ground return to battery.  If the attendant saw a 
>jar bubbling, he took his shotgun and went down the street to 
>investigate.  Forget about calling the cops; the telephone was still 
>a long way off.  The alarm service was also an armed guard service.
>
>And as we say in Chicago, all this and a buck fifty will get you a 
>ride on the subway.
>
>Party on.=
>
>Uncle Ben=