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TonyDuell · 1st Oct 2019, 7:13 pm

Ones I need to get round to figuring out (I have the units -- too many projects I guess)

Modem 2B (large box with plug-in modules -- power supply, modulator, demodulator, control, all discrete transistors and relays) 300 baud originate and answere

Modem 13B (Plinth under a 700 telephone, also 300 baud originate/answer)

D1200A. May not be GPO, but in the same case as the Modem 2B with similar modules This is the host-end modem for a prestel connections (75 baud receive, 1200 baud transmit).

And one I have done, in that I have reverse-engineered the circuit diagram and understand how it should work :

Modem 13A : Plinth under a Telephone 740, 300 baud originate only.

I would be happy to send said hand-drawn reverse-engineered diagram to anyone who wants it.

1st Oct 2019, 7:13 pm	#5
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: GPO Modems Ones I need to get round to figuring out (I have the units -- too many projects I guess) Modem 2B (large box with plug-in modules -- power supply, modulator, demodulator, control, all discrete transistors and relays) 300 baud originate and answere Modem 13B (Plinth under a 700 telephone, also 300 baud originate/answer) D1200A. May not be GPO, but in the same case as the Modem 2B with similar modules This is the host-end modem for a prestel connections (75 baud receive, 1200 baud transmit). And one I have done, in that I have reverse-engineered the circuit diagram and understand how it should work : Modem 13A : Plinth under a Telephone 740, 300 baud originate only. I would be happy to send said hand-drawn reverse-engineered diagram to anyone who wants it.