TELECOM Digest OnLine - Sorted: Re: Los Angeles Step by Step - Network Management (H

Re: Los Angeles Step by Step - Network Management (H

Sam Spade (
Sun, 30 Jul 2006 01:16:08 -0700 wrote:

> Early on (1920) the Bell System realized step-by-step would be
> inadequate for big city high calling volumes and developed and
> implemented panel switching for cities. However, Los Angeles already
> had step-by-step when Bell took over.

> As Los Angeles/southern California grew in the war years (big defense
> aircraft plants, new postwar development), how did they handle the
> high volume traffic with step-by-step? Did they run into problems?
> SxS switches are limited to a 10x10 pattern and get very unweildy when
> it grows beyond that. I could imagine things got messy in the early
> 1960s before ESS was available. Were some SxS offices upgraded to a
> more powerful No 5 crossbar?

> The Bell Labs says they considered developing common control senders
> as a front-end to SxS, but I didn't understand how far they went with
> that. They also did something called a "graded multiple" which
> apparently was a big help.

> In the early 1950s NYC got network management, a control center for
> city wide traffic. It seems the Los Angeles area would need likewise
> in the 1950s or early 1960s.

> Thanks.

> [public replies, please]

The steppers were not allowed to grow that large. There were multiple,
separate SxS machines in the largest office, downtown LA and perhaps
Hollywood. Most of the defense plant areas were served by General

Pacific Telephone installed at least one No. 5 Crossbar in each large
SxS office on a rather rapid basis after the war. These units served
as the common control unit for toll and the SxS machine (or machines)
in the building fed into the No 5 machine for toll routing. The No. 5
machines were also often used as a local machine as well, providing
much better line services for preferred customers.

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