Talk:Plan 55-A

Basic article

Wrote a basic article. Think of Sendmail, built out of paper tape punches and readers interconnected via a telephone switch. More later; there's a video in the Internet Archive if I can find it again. --John Nagle (talk) 05:35, 12 March 2009 (UTC)[reply]

Video in "Telegram for America".[1]. Cloying movie, but some footage of a Plan 55-A switching center. --John Nagle (talk) 05:48, 12 March 2009 (UTC)[reply]

was this thing really around in 1948?

1948 seems far too early for something like this to have been in use and, as far as i can tell, the single reference cited for that date is unrelated to plan 55-a. according to this article from the western union technical review, plan 55-a was new technology as of april 1958. --Communeofone (talk) 10:09, 27 July 2012 (UTC)[reply]

You may be right. There's a 1948 patent, #2632044, which describes a Western Union reperforator-based message switching system. But it requires operators to push a button to route each message. I think that's Plan 21-A, but I'm not sure. "Telegram for America" (1956) shows fully automatic forwarding on main lines, with push-button forwarding further out on the network. So automatic forwarding was working for WU by then. Keep looking for the first automatic forwarding system. It looks like Plan 55-A was the military version, with security, precedence, and other military features. --John Nagle (talk) 21:36, 5 April 2013 (UTC)[reply]

See "The Development of Western Union Switching Systems" (1948)[2]. That has a description of switching up until then. There was a little automatic forwarding by 1948, but only in certain special cases. Push-button semi-automatic routing was deployed to all major centers by 1948, but there were still some cord boards and some torn tape positions. That paper also explains Plan 21-A. More Plan 21-A details in the 1949 sequel to that paper [3] Plan 21-A was about half push-button switching and about half fully automatic. The previous all-pushbutton system was called Plan 20. --John Nagle (talk) 21:54, 5 April 2013 (UTC)[reply]

By late 1950, Western Union had 15 major Plan 21-A area switching centers handling most of the long distance traffic. Most messages went through those fully automatically. The equipment required filled multi-story buildings. So by then, WU had full-auto message switching working. It just hadn't been deployed to the smaller stations yet.[4] --John Nagle (talk) 22:20, 5 April 2013 (UTC)[reply]

I'm reading through all those WU Tech Review issues. They mention Plan 1 (for Morse code switching), Plan 31, Plan 51, etc. Each year, the system became more automated. General Electric got an in-house Plan 51 system in 1948, which was initially a fully automatic message switching system with 7 centers and 149 endpoints, along with an interconnection to the larger WU system.[5] John Nagle (talk) 05:04, 7 April 2013 (UTC)[reply]

Plan 21-A

There was an earlier system, a "Plan 21-A" [6] but a reliable source is hard to find. The Smithsonian may have some records.[7]. --John Nagle (talk) 19:52, 12 March 2009 (UTC)[reply]

I'm pretty sure the "55" refers to "1955"

I went to the Air Force Plan 55 in 1958, conducted by Western Union in Chattanooga TN. I think we were told that 55 referred to the year. Whether this was the year of design, or year the contract was let, I don't know.

One feature of the Plan 55 system was the "Loop Gate Transmitter." See US Patent US 3033925 A

Filing date was given as 2 Dec 1958 (At which time, interestingly, I was in their school!)

See http://www.google.com.na/patents/US3033925

104.244.216.181 (talk) 01:43, 10 September 2015 (UTC)[reply]