Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!bu.edu!telecom-request From: john@zygot.ati.com (John Higdon) Newsgroups: comp.dcom.telecom Subject: Re: Headset Installation Help Needed Message-ID: <74372@bu.edu.bu.edu> Date: 9 Feb 91 18:43:00 GMT Sender: news@bu.edu.bu.edu Reply-To: John Higdon Organization: Green Hills and Cows Lines: 29 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 11, Issue 105, Message 4 of 7 Daniel A. Margolis writes: > Also, not all phones are compatable with all headsets. I've seen "headsets > for standard phones," "headsets for electronic phones," and "headsets for > multi-line phones." I don't know what the difference is. One of the major differences concerns how the transmitter (mouthpiece) is handled. In an ordinary telephone with a carbon transmitter, a small amount of the loop voltage is used to "polarize" the microphone button. A carbon unit is simply a voice activated variable resistor that modulates a current flow at an audio rate. The result is fed down the phone line as a representation of your speech. Some newer (electronic) phones do not use a carbon mic but employ a "dynamic" microphone (similar in construction to the earpiece) that does not require a polarizing voltage. Instead the signal is amplified using a line-powered amp in the instrument and that signal represents your speech. Obviously, the two types of transmitters are incompatible. Plantronics solves the problem by providing a special interface for use with "dynamic mic"-type phones. A cube transformer plugs into the wall and provides the polarizing voltage (which is missing in the electronic phone) for the headset. John Higdon | P. O. Box 7648 | +1 408 723 1395 john@zygot.ati.com | San Jose, CA 95150 | M o o !