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From: zygot!john@apple.com (John Higdon)
Newsgroups: comp.dcom.telecom
Subject: The Way It Used To Be
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Date: 10 Aug 89 02:40:37 GMT
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X-TELECOM-Digest: volume 9, issue 285, message 1 of 11

Something that every reader of this group should do is take a tour of a
local central office. I would kill for that opportunity now with all
the advances in the past few years such as COSMOS, electronic
switching, etc. But I never will forget the several times I toured
local offices, both officially (with a public tour) and unofficially
(with a friend who was a supervisor in the office).

The Santa Clara "AXminster" office used to be exclusively #1 and #5
crossbar. There was a big ammeter in the power room that indicated the
draw from the 48V batteries by all the equipment in the building. Late
at night (when I was there) it read between 2000 and 3000 amperes. The
copper bus bars carrying this current were enormous. I was told that
during the day the typical indication was around 5000 amperes. A good
portion of that draw was simply to supply loop current to the thousands
of subscribers who were off hook, and of course the rest went to power
the zillions of clattering relays.

There was a room with a bunch of little odometer-like counters,
thousands of them. While I was standing there, suddenly the lights went
out, there was a flash, and then the lights came back on. They actually
photographed the dials for traffic studies. Long distance call records
were kept on paper tape that was handled by these large floor standing
machines. Near one of the test positions, was a machine that would
periodically make a lot of noise and then a punched card would drop
into a basket. This was the "trouble recorder" and the card would
contain information concerning some error that occurred within the maze
of electromechanical equipment.

Ringing current was generated by these rotary devices that produced the
ringback tone and busy tone as well. Before touch tone, they also
produced dial tone. The cadence was performed by these mercury-filled
drums that were driven off the same shaft as the ring generator.

The #1 crossbar bit the dust several years ago, but the #5 remains.
The old panel equipment that was in the now-defunct
Larkin Street CO in San Francisco has been preserved by the local
chapter of the Telephone Pioneers and will still operate upon request.
Again you must see this equipment operate to appreciate how it used to
be. If you live in an area that still has functional electromechanical
CO equipment, do whatever it takes to wangle a tour before it's all
gone forever.
--
        John Higdon         |   P. O. Box 7648   |   +1 408 723 1395
      john@zygot.uucp       | San Jose, CA 95150 |       M o o !