Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!uwm.edu!cs.utexas.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request From: john@bovine.ati.com (John Higdon) Newsgroups: comp.dcom.telecom Subject: Re: Panel (ugh!) Switches Message-ID: <8250@accuvax.nwu.edu> Date: 25 May 90 05:20:27 GMT Sender: news@accuvax.nwu.edu Reply-To: John Higdon Organization: Green Hills and Cows Lines: 47 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 10, Issue 384, Message 7 of 11 Jack Winslade writes: > I've been fascinated with the panel switches (Ma Bell's answer to Rube > Goldberg) ever since seeing an aging one in action back in 1971 or so. Panel was almost universal in San Francisco and Oakland up until the early 70's. Obviously, exchanges added in the '50s onward were crossbar and later, ESS, but there was a substantial penetration of these impressive machines. Having grown up in Oakland, I'll never forget the sound of the phone. > If I remember my facts correctly, the revertive pulse-counting method > was necessary because the speed of the rollers driving the rods up the > frames was not exact, and this provided the feedback necessary to > locate the correct contacts. That is correct, and it also accounted for the horrendous noise that you heard, particularly between dialed digits. These rollers would slip and slide, even with heavy maintenance. Sometimes the rods couldn't make it to their destination, and the call would fail. This is why the switch was so unreliable. > Another thing that I found peculiar to this particular installation > was that an adjoining #1 crossbar office was also equipped with this > type of revertive-pulse sending system, which made the crossbar office > look like a panel office as far as interoffice signaling was > concerned. This was a typical situation: panel offices were usually neighbored by #1 crossbar because they could be made to speak the same language, revertive pulsing. The down side of this was that panel was particularly incompatible with SXS, which is one reason you would have a lot of panel in an area (such as SF/Oakland) OR you would have a lot of SXS (such as LA). Fortunately, the crossbar became a life saver in that it could speak equally well to SXS or to panel and frequently served as a translating link between these offices. BTW, to the best of my knowledge, the Telephone Pioneers of San Francisco have a small, fully operative, section of a panel office somewhere in San Francisco. For a while it was located in the old Larkin St. CO, but I believe it has moved from there. (How on earth would anyone move such a thing?) John Higdon | P. O. Box 7648 | +1 408 723 1395 john@bovine.ati.com | San Jose, CA 95150 | M o o !