From: "Ed Price"
References: <firstname.lastname@example.org> <email@example.com>
Subject: Re: It must be christmas time
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Thu, 28 Nov 2002 14:58:50 GMT
NNTP-Posting-Date: Thu, 28 Nov 2002 09:58:50 EST
Organization: Cox Communications
"John Larkin" wrote in
> On Wed, 27 Nov 2002 16:46:30 GMT, Spehro Pefhany
> I remember an old electromechanical telephone dial exchange in my
> neighborhood when I was a kid. It used 2-axis mechanical stepping
> relays; Strowger relays? It was cool inside, like being surrounded by
> machine guns. The guys who ran it used to let us wander around inside
> and steal wire. We also used to take the bus to the airport, MSY,
> where they'd let us wander around in the control tower and radar
Those mechanical switches were the Strowger system, invented by a mortician
named Strowger (the story goes that he was incensed by human operators
taking a payoff to route calls to his competition, so he invented a system
to take the humans out of the loop).
The system is also called the "up and around", descriptive of how the
mechanical switches step to make a connection. I believe that each switch
had ten banks of ten contacts. As you dialed a number, the switch would step
in unison with the 10 Hz interrupter switch in your phone dial. The first
number would step the switch armature "up", then the second number would
step the switch armature "around." Then another switch would handle the next
two dialed numbers. When the call was terminated, the switches would do an
automatic cycle to their "home" position. A large matrix of these must have
been impressive, and noisy! Those were extremely high-rel mechanisms (IIRC,
they had 4 redundant wiper arms per contact), but the armature was still
rather heavy, and was moved by a series of solenoids, ratchets and cams.
IIRC, the switches were made by a company called Automatic Electric.