Info about Z80 machine

On Mon, Sep 23, 2013 at 12:40:17PM -0700, Chuck Guzis wrote: [...] In theory, the top speed of your modem. A VoIP ATA is after all doing exactly the same job as the line card in your local telephone exchange, except without miles of manky old copper in the way. Practice, of course, is another matter. I know, because I tried it. It was far too ambitious a project as the calling leg was GSM, and it also went over a relatively slow ADSL line before being terminated on a modem that had already had a very hard life. But hey, we like a good challenge :) The outgoing GSM leg was 9600bps CSD, although the mobile telco converted that into a V.34 call to my VoIP number for no obvious reason. V.34 wouldn't work at all: it'd just squeal away negotiating lower speeds until giving up. I fiddled with a whole load of S registers to disable modulation schemes that might be latency-sensitive, and eventually got it to sort of hold a connection at 7200bps. Had I *two* modems, I would have expected it to just work across my LAN.