TIPE Project


Posted on Feb 5, 2014

A simple non-commercial grade multiplexer compatbile with telephones. It will supports 4 telephone lines, and will multiplex over one cable. The topic was free of choice, but had to be oriented aroudn the theme of `PrG©vision` (prediction). As you may have guessed, I chose `Multiplexing` as my topic subject. I`m hoping to learn a lot on my way, since I``m not very experienced in the field of electronics (I once tried to


TIPE Project
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design a 65C02 based computer, but never got past the design stage. ), not in the field of teaching, so this page may come across as confusing in some places. I`d go with a 65C816, but I feel that for this project, something simple, and quick will do, even if I do have to pay more somewhere else for this "mistake". I`ll be modulating the voices with PCM, which means I`ll be sampling 8 bit audio at 8000 samples/second. The 65C02 will be able to apply the A/ µ law (dynamic range compression codec ) while it`s not sampling or resending data to the multiplexer. I`m hoping to run the CPU at 2 or 4 Mhz in order to be able to sample and retransmit information in a timely fashion and to be able to apply the "compression". I need to learn more about phone lines and impedance in order to fully understand what echo cancellation is, what wet transformers are and so forth, as this will be essential in determining how I am going to be interfacing DAC/ADCs to the phones. As anyone may know, a telephone line is composed of a long pair of copper wires (also called a twisted pair under some cases, when they are twisted around each other to avoid interference). Depending on the length, gauge and size of these wires, they respond differently to signals: impedance. In this case, we have to take into account complex impedance modelized as (resistance, Res; and reactance, Rea): Z = Res + jRea, where j is the "imaginary" number. In the case of...




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