The Telecom Digest for November 22, 2010
Volume 29 : Issue 315 : "text" Format
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Date: Sun, 21 Nov 2010 10:18:40 -0800 (PST)
From: Lisa or Jeff <email@example.com>
Subject: On preliminary false switchhook pulsing
I checked the Bell Labs history ("Switching, 1925-1975") to see what
was said preliminary false switchhook pulsing. There wasn't much, and
I couldn't find anything in the 1875-1925 book.
For SxS offices:
"arrangements were developed to prevent wrong numbers due to
preliminary pulses which might be falsely generated at the start of a
call when the receiver is first taken off hook. This also resulted in
the standardization of 11X service codes compared with X11 for the
Ref: "Counteracting Dialing Errors in the Step by Step System", Bell
Labs Record, January 1929, p 198.
To add long distance to an SxS office on the basis of area code (0/1)
would've been expensive due to adding senders/registers or building
out the switch train. The easier way was to add 1 as a prefix. "An
exception was the elimination of preliminary pulse detection, a
feature that was abandoned with the obsolescence of the desk stand
* * * *
I am not sure why panel switching didn't have the problem that SxS
since both systems in their early days used desk-stand (candlestick)
Unfortunately, I don't have easy access to library issues of Bell Labs
Record to study this further. I hope someday they put the record on
line; it would answer many historical questions.
Date: Sun, 21 Nov 2010 14:49:34 -0500
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