Theo v. Werkhoven wrote: ^^^^^^
ITYM 1986.. In '68 there weren't even modems around yet afaik, only TELEX and Telegraphy. The computers in those days were al in hands of large coorporations, and all worked on either dedicated tasks or with batched processing of punch cards or paper-tape. If they even had a terminal it was a teletype kind of console, just for the demi-god Operator, no-one else.
There were modems in 1968, though they tended to be proprietary, expensive and scarce. I started working in the telecom industry in 1972 and there were certainly 2400 bps modems available then. Also, the industry used devices called "voice frequency carrier telegrahpy" for decades, which were essentially a bank of modems, each tuned to different frequencies that allowed several teletype circuits to be carried over a single voice circuit. Some of the ones I used to work with, were so old they were built with vacuum tubes! The VFCT systems were also available in a single channel configuration, which would be comparable to a "modem". The use of tones to multiplex data channels, goes back to A.G. Bell and predates his telephone work.