Western Electric Model 551(B) Private Branch Exchange:


We've all been enthralled by tales of the original Phone Phreaks -- Captain Crunch, Steve Wozniak, and the Blue Boxers of Yore.

This years entry in the RetroChallenge takes a look at telephone switching equipment through the years and will involve a Western Electric Model 551(B) PBX System with a patent date of 1927 and components dating from the early 1930's. No, this is not a computer. No, the PBX itself is not Turing Complete, nor does it contain anything that could be described as a Central Processing Unit. It does, however, share a number of similarities to "modern" data processing equipment and even used a common artifact of the computer age -- the ubiquitous Punch Card.

My goal is to make this particular system "Work" -- not just to serve as a simple telephone answering point, but to examine the overall structure of the public-switched telephone network and see how it evolved from a simple manual switchboard.

Western Electric Switchboard

Western Electric Model 551(B) Private Branch Exchange (Circa 1927)

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This web-page created on August 15, 2021 by Micheal H. McCabe. Last updated 10/31/2021 Original URL is http://phreak.paleoferrosaurus.com/