larry@uunet.uu.net (Larry Lippman) (09/14/89)
> In article <telecom-v09i0371m03@vector.dallas.tx.us> clements@bbn.com writes: > As long as we're reminiscing about SxS exchanges and tours and such... [description of routing translator for No. 4 toll tandem office...] > Each such inquiry resulted in a large "WHAM!" as a bunch of solenoids > shoved huge trays of metal cards around. The selected card had > the answer punched in it. The cards were metal because of the great > number of read cycles. Updating the routing consisted of punching a > new metal card and replacing the old one in the bin. Every once in > a while there was a distinctive "WHAM-WHAM!" in among the many > random "WHAM!"s. We were told that was a "come-again-six" operation. > That meant that the three digits weren't enough to select the trunk > group - say 603 for NH - and the "ABC" code (3 digits after the area > code, total six) were needed. The equipment holding the number > had to "come again" (request another cycle) with the rest of the six > digits. There was one redeeming feature of the above mechanical monster: the routing cards were read optically using light beams and photocells, which was pretty state-of-the-art - for 1950, that is. The outputs of the photocells had to drive relays to convey the translator information to the marker. Now, knowing WECO design philosophy as I do, I would bet that those photocells were either of the selenium photovoltaic variety and directly drove a damn sensitive relay (like a 280-type polar relay), or they were of the cadmium sulfide photoresistive variety and drove a relay using a cold cathode tube. Ain't likely that WECO would have used an electronic circuit using a conventional vacuum tube as an amplifier to drive a relay. ANYTHING but a conventional vacuum tube in a piece of WECO switching apparatus! :-) Mechanical monsters of the 1950's and 1960's which rival the above routing translator were the massive CAMA perforators and readers. Three-inch wide punched paper tape on 2-foot diameter rolls were something to behold! > Some of this gear used plunger line switches that were so old that > they weren't even "restoring". A plunger line switch is a wonderful > device which can't be described without a diagram. It performs the > function of a Strowger "Line finder". The plunger switch was invented by A. E. Keith in 1906, who was a founding father of Strowger Automatic Electric. It is also sometimes referred to as the Keith Line Switch. The invention of this particular device was a vital achievement which simplified previous designs of SxS switching apparatus. The 200-point linefinder as we know it today was invented in 1928, and rapidly replaced the Keith Line Switch. The linefinder was such a vast improvement that the Keith Line Switch was obsolete by 1930. Whatever apparatus you had was probably built before 1930! > Grasshopper fuses; yuck. While it was relatively uncommon, the 35-type "grasshopper" fuse could actually be repaired by replacing the fuse wire! A LOT of 35-type fuses were repaired during World War II when materials were scarce. Can you think of a more boring job for a switchman? <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> TEL 716/688-1231 | 716/773-1700 {hplabs|utzoo|uunet}!/ \uniquex!larry <> FAX 716/741-9635 | 716/773-2488 "Have you hugged your cat today?"