telecom@ucbvax.UUCP (12/26/85)
I am investigating the electrical characteristics of current telephone handsets and speakers. (It used to be easy, but these days you can't count on having a carbon button mike and a ring-armature earphone!) I would like to know the following. 1. Which transducers are the major suppliers of telephones for commercial applications (such as AT&T, ITT, GTE, TIE, etc) using in their handsets and speaker phones? Also, who are the manufacturers of these transducer units? 2. What are the advantages and disadvantages of these newer transducers over the standard units (carbon button and ring armature)? 3. What analog signal processing occurs in electronic telephones? 4. Where can I get technical details (such as magnitude and phase response, harmonic distortion, and directivity) about these transducers? On a different topic, how do PBXs, local loop circuits, and long distance circuits affect analog voice channels. I am particularly interested in identifying the types of circuit or switching that do the following: (1) distort the passband frequency response, (2) distort the envelope delay, and (3) add transient phenomena, such as impulse noise or dropouts. I would appreciate specific information, references, pointers, etc. Thanks for you help. David Burton Entropic Processing Inc. USENET: ...!{seismo | decvax}!epiwrl!burton ARPANET: epiwrl!burton@seismo.ARPA
telecom@ucbvax.UUCP (01/04/86)
I hate to type, and the subject you ask about is quite complex, but if you care to call, I will try to help. You can reach me at Digitech Communications, Inc. (we manufacture telephone central office equipment). (205) 533-5941 office, (205) 882-0503 home. Call any time. Roger Atkinson