On 2017-May-09, at 9:06 AM, Chuck Guzis via cctalk wrote: > Looking at this documents: > > http://www.samhallas.co.uk/repository/telegraph/data_set_101c.pdf > > I sill can't figure out what a lot of the stuff inside is for.
I've looked at one of these modems in the bottom of a 33 although not examined it in great depth. I expect a large part of the volume of stuff like the relays isn't really modem but call-management sequencing & switching: on/off hook, incoming-call detect, answer detect, originate/answer mode switching, etc. Going from examination of another modem from the era, the modem proper can be expected to be on the several PCB cards, modularised as filters, modulator, discriminator, 20mA loop interface, etc. The telephone equipment manufacturers in those days were very good at laying out and wiring things in an exceedingly complex manner, they really liked wire bundles and dress.
