In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Peter Van der Zee wrote:

Hi William;

I can probably answer part of your questions, and maybe give some insight into some other issues.

Years ago (pre SX) I built a commercial hardware rendition of what can now be more easily done with software and it worked amazingly well.

1. Yes the SX is fast enough; you may want to design it in a "scalable" form; one SX per line/channel

2. If the sample rate is high enough (upwards of 8 K samples/sec) the quality is good. To increase sampling speed while reducing the amount of data to be transmitted, we used the "Continuously Variable Differential" encoding method. This was done in a (Philips?) chip, but you should be able to come up with some really good software agorithms. (You lucky guy......I have been wanting to try this for a long time). You also will want a logarithmic amplitude encoding scheme, A-law or U-law.

3. Don't know, as best as I can recall we used no hybrids yet had good results.

4. It is very ambitious if you are looking for commercial quality results. If it is just for yourself and non-commercial, then you can eliminate the regulated default "POTS" 
requirement, and put up with whatever "features" you want.

Great project, have fun.

Peter (pjv)

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