>Date: Wed, 5 Aug 1998 10:18:16 -0400 >From: "Victor L. Boersma" <[email protected]>
>In TIA TR41, the proposal was made several times to write such a >standard, but it never got off the floor. The good design of a >voice switch (the way in which the device determines whether to >process incoming signals or whether to ignore the incoming >signals and allow transmission of outgoing signals) is a very >intricate matter and those who believe they have the best voice >switch(es), are not eager to part with that intellectual property. You're absolutely right! When I worked for GTE's internal quality control laboratory we tried to come up with our own "qualification test suite" for speakerphones -- we never succeeded. Just too many unknowns - it wasn't sufficient to merely measure the speed at which a speakerphone could switch from transmit/receive, or how it performed with known levels of background noise being injected into the inputs. All our test data never really gave any clear indication of what phones worked/sounded the best in real life situations. We finally just did comparison testing where we used "panels" of people who talked over the various models. The most ususual speakerphone I tested was a big "desk blotter" which had a raised hump along the right edge which contained the keypad and other controls. There were two speakers, one at either side of the back of the desk blotter in a raised lip, and two microphones which were mounted at either side of the front of the desk blotter (very close to where the person using it would sit). This speakerphone DID NOT SWITCH -- it was full duplex, sending and receiving at the same time! The wide (and fixed) separation between the speakers and the microphones prevented any "singing" (telco term for oscillatory feedback <g>), and it was an excellent speakerphone. Unfortunately, this $1000 phone failed the "coffee test," i.e., the keypad wasn't liquid proof, so the first time a drink was spilled on the desk blotter, no more speakerphone! <g> ________________________________________________________________ John Combs, Senior Project Engineer, ITS/TestMark Laboratories Email: [email protected] URL: http://www.testmark.com
