when ~50kbps was regarded as close to the maximum possible, with learned quotes about line bandwidth and Shannon's theorem to back them up

all of which were true for audio based data transmission

Sending RF down the phone wires changed the rules.

In reply to a post by yarwell:

Sending RF down the phone wires changed the rules.

Not really... there's no fundamental difference between RF and AF, they're just convenient human-oriented labels, the electrical equations are identical.

But I'll agree that techniques that can be used at RF may well not be practical at AF.

there's no fundamental difference between RF and AF

other than the frequency, of course. The previous "56k" limit was for use of audio band only with transmission over the phone voice system - it wasn't improved upon - not least because the digital exchange only had 64k fo bandwidth per circuit to carry the modem traffic to the ISP.

So I would argue the 56k limit was and is correct for its context. Putting new kit into exchanges and allowing the use of more frequencies changes the limits and the bandwidth that can be considered.

I worked on "RF" down at 10kHz and below. Data rates were a little low but ranges were quite impressive!

In reply to a post by TheHorseman:

In reply to a post by boxst:

I was still happy of course with that as I am old and started running a bulletin board with 300 baud...

Steve

Yes, I started off with an old ex BT 300 baud modem. The computer I had at the time did not have a terminal program, so I wrote one complete with built in dialler. (I think the computer was possibly my old Video Genie).

Woo, a modem I started with an acoustic coupler and buying access to the computer at Imperial College. Mind you it was 1976.

Teletype to an acoustic coupler somewhere between 1970 and 72. Writing a commercial program in Basic. In Manchester, talking to a bureau in London.

In reply to a post by simon194:

In reply to a post by TheHorseman:

In reply to a post by boxst:

I was still happy of course with that as I am old and started running a bulletin board with 300 baud...

Steve

Yes, I started off with an old ex BT 300 baud modem. The computer I had at the time did not have a terminal program, so I wrote one complete with built in dialler. (I think the computer was possibly my old Video Genie).

Woo, a modem I started with an acoustic coupler and buying access to the computer at Imperial College. Mind you it was 1976.

The ex BT modem I had was large, I think it was intended as a 19" rack mount job. It weighed a fair amount too. I had just encountered computers in '76 as that was when I started my second job (and I'm still there just over 36 years later).

I don't feel quite so old now