> That's true. I felt the original posting implied that Hayes invented
>> something entirely new; which wasn't quite true.
> As far as I know, his was the first modem to use in-band signalling.
> It was really rather clever to build a UART into the modem and use it
> to let the computer control the modem over the same channel as it used
> to communicate with the remote system.
> In-band signalling has its problems (that's what made blue boxes
> possible) but in this case it let people hook up modems to their PCs
> using a cheap generic serial interface.
> R's,
> John
Dial modems that accepted dialing commands over the RS232 interface did exist prior to Hayes (Codex and Vadic at least). What Hayes did was improve the concept and patent the +++ escape sequence in
1985. Most prior modems could not go back to command mode without disconnecting from the call, using "Long Space" disconnect. Also he targeted the then-new PC market with a low cost unit. Codex etc were considered corporate business-class modems priced accordingly.--Reed