Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request From: Christopher Owens Newsgroups: comp.dcom.telecom Subject: Re: 500/2500 Handsets Message-ID: <11196@accuvax.nwu.edu> Date: 21 Aug 90 18:12:34 GMT Sender: news@accuvax.nwu.edu Reply-To: Christopher Owens Organization: University of Chicago Lines: 20 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 586, Message 4 of 11 In article <11093@accuvax.nwu.edu>, roy@alanine (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? The microphones on 500/2500 handsets were (still are?) made using a pellet of tightly-packed granulated carbon as the transducer. These pellets go bad (mechanical wear? environmental contamination?), resulting in lousy fidelity. A phone in this state can often be brought back to prime condition for a short while by giving the handset a rap on the desktop. But eventually the microphone needs to be replaced. It's about the only part of a 500 or 2500 that doesn't last forever. Someone at Bell undoubtedly decided that, since they expected to own the phones forever, the money spent at the factory on the drop-in mount would be more than paid back in savings of the repairman's time.