[GreenKeys] Fire Telegraph

[Keith Lueck]

In the early 90's, I worked on a consulting job for an alarm central station that used the McCulloh signaling system.  IIRC, it used two wires, and reversed polarity for marking and spacing, so the receiver could detect a fault in either line.  The receivers used 3/8" paper tape, and when one went off, the operator had to go and "read" the paper tape and look up the code - just like what's depicted in the film.  Even back then, they were having trouble finding sources for the paper tape (sounds familiar, eh?).  These were all "legacy" accounts that hadn't switched to more modern signalling systems.  The receivers themselves looked like they dated to the 60's.  There were a couple dozen receivers and some had hundreds of alarm points connected to single receiver's line.  There was a 48V battery room that powered the McCulloh signalling, and they had a backup generator for the other equipment.   There was a set of auxiliary dry contacts on the receiver that mimicked the received marking/spacing  that I was reading with a PC to automate the system.  The PC looked up the code, determined the customer / location, and notified the operator, who verified the alarm and called the fire dept. or police.  It was somewhat challenging b/c most of the transmitters used clockwork mechanisms and the transmission rate varied widely - sometimes even during the course of a transmission.  Codes were set at the alarm point by breaking teeth off a nylon or bakelite wheel - a lot like one bit of an answer back drum.  Of course, there were lots of UL hoops to jump through.  Everything had to be UL listed.  Finding a UL-approved surge suppressor for ethernet cables before the days of the internet was quite a challenge...
      From: Nick <creativegardening at hotmail.com>
 To: "GreenKeys at mailman.qth.net" <GreenKeys at mailman.qth.net> 
 Sent: Monday, November 27, 2017 8:13 AM
 Subject: Re: [GreenKeys] Fire Telegraph
   
#yiv6533930397 #yiv6533930397 -- .yiv6533930397EmailQuote {margin-left:1pt;padding-left:4pt;border-left:#800000 2px solid;}#yiv6533930397 Very impressive, especially the effort and manpower to help others. 
Nick  -  N0NCQ 


Sent from my T-Mobile 4G LTE Device

-------- Original message --------
From: Richard Knoppow <1oldlens1 at ix.netcom.com> 
Date: 11/27/17 12:31 AM (GMT-05:00) 
To: greenkeys at mailman.qth.net 
Subject: [GreenKeys] Fire Telegraph 

    A video on You Tube shows a c.1920s fire alarm system in Brooklyn N.Y.

https://www.youtube.com/watch?v=dQLlJVagmOs
-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL
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