Date   : Mon, 25 Jan 2021 18:02:34 +0000
From   : pete@... (Pete Turnbull)
Subject: Completely expanded "Cheese wedge" BBC Micro - just

On 25/01/2021 14:16, Chris Johns wrote:
> I had rather expected the prestel adapter to be not much more than a
> modem in a cheese wedge. Was there more to it than that?

It has an autodialer.  However the mandate was to build a simple dumb 
modem without any sort of processor, so it had to use a state machine to 
change modes and do things like going on/off-hook, dialling, etc. 
Unlike devices such as Hayes Smartmodems which use an ASCII command set 
to control smart functions, or other modems that use the user port or 
some other signalling interface for control, only the Tx, Rx, RTS and 
CTS lines from the RS423 interface were available to control it.

-- 
Pete
Pete Turnbull