larry@uunet.uu.net (Larry Lippman) (08/24/90)
In article <11093@accuvax.nwu.edu> roy@alanine.phri.nyu.edu (Roy Smith) writes: > OK, here's a question that's been bothering me for probably > about 20 years. Why, on a standard 500/2500 handset, does the > microphone just drop in but the speaker have screw terminals? That's a pretty good question! In attempting to give you a reasonable answer, I must first point out that some telephone handsets did have drop-in receiver elements. For example, the WECO 300-type telephone set used the F-type handset, which used the HA-type receiver. The HA-type receiver was of the drop-in variety. Some older operator headsets, like the 51-type and 52-type use the HC-type receiver which also drops in place. Other vendors of telephone apparatus, such as Automatic Electric, Northern Electric (pre-Northern Telcom days), and Stromberg-Carlson also had telephone handsets which used drop-in elements. The introduction of the WECO 500-type telephone set around 1953 with the G-type handset created a departure from drop-in receiver elements. There is no singular reason why the G-type handset, using U-type receiver elements, no longer employed a drop-in receiver. The reasons are multiple, and include but are not limited to: 1. The receiver element was now more reliable, and therefore much less prone to failure and replacement. Better varistors across the receiver element, and additional varistor loop current limiting in the "newer" 425-network (as opposed to 300-type sets) resulted in less likelihood of overcurrent and failure of the receiver element. 2. Eliminating the receiver element drop-in contacts resulted in a cost reduction. 3. Eliminating the receiver element drop-in contact assembly resulted in a size and weight reduction of the G-type handset over its F-type predecessor. 4. Eliminating the receiver element drop-in contacts resulted in an elimination of failure or noise as a result of receiver element contact corrosion. The carbon transmitter, however, was still a source of potential failure, and therefore remained as a drop-in device for ease of its replacement. BTW, when is the last time that anyone saw a 300-type telephone set in service? Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" {boulder||decvax||rutgers||watmath}!acsu.buffalo.edu!kitty!larry VOICE: 716/688-1231 || FAX: 716/741-9635 {utzoo||uunet}!/ \aerion!larry [Moderator's Note: Last 300 phone seen, about five years ago, admittedly in an obscure location: The clock and bell tower of Holy Family Church on West Roosevelt Road. A tiny room in the tower, rarely visited, where the clockworks was located. The phone was probably for use by the men who did the repair work on the clock and bells or the sexton, from the days when the clock had to be wound with a crank. The phone did operate; it was an extension of a line in the office downstairs. On the bottom was penciled in a date in 1938. PAT]
dave%westmark@uunet.uu.net (Dave Levenson) (08/27/90)
In article <11248@accuvax.nwu.edu>, kitty!larry@uunet.uu.net (Larry Lippman) writes: > BTW, when is the last time that anyone saw a 300-type telephone > set in service? About ten minutes ago! Where? At AT&T Bell Laboratories, Whippany, NJ! They are hung on the wall, next to the house fire alarm boxes, at most of the intersections of the corridors in the older sections of the building. Heavy-looking black rotary-dial wall sets with F-type handsets. I'm not sure who is supposed to use them, or under what circumstances. I think they are part of an old house-phone system that pre-dates Centrex and pre-dates the walkie-talkies that are now carried by the AT&T building maintenance and security forces. Maybe someone who works there can tell us why. Dave Levenson Voice: 908 647 0900 Fax: 908 647 6857 Westmark, Inc. UUCP: {uunet | rutgers |att}!westmark!dave AT&T Mail: !westmark!dave [The Man in the Mooney]