Although we don’t know how good echo suppressors can get, we do know
that a long circuit with the best possible suppressors could never be
_better_ than a circuit of the same length that had no echos. This
brings us back to the problem of how serious the effect of delay alone
is on conversations. If the delay in a synchronous satellite system,
even without any echo, made conversation all but impossible, there would
be little point in developing echo suppressors for such satellites.
This question looked like one that we could answer, at least in part, by
experimenting with special four-wire circuits that had delay but no
echo. The strategy we adopted, then, was to do some experiments on pure
delay while other people at Bell Telephone Laboratories began to attack
the problem of testing and improving echo suppressors. In the pages that
follow, I will describe one of our experiments on the pure delay
problem. More elaborate ones have been performed since, and there will
be more to come.
It should now be clear how this sort of experiment might be helpful to
the development of a synchronous satellite communications system. If it
showed pretty convincingly that conversation was extremely difficult
with a pure echo-free delay of about a second, synchronous satellites
for two-way conversations would be less practical. On the other hand, if
the experiment were to show that some conversation, at least, could be
carried on without too much difficulty, our results would be less
decisive. We would know only that _echo-free_ delayed circuits might
_sometimes_ be all right. But we would not know how bad they were under
a variety of conditions or how closely they resembled a real circuit
with echoes and echo suppressors. In either case, the experiment would
have no bearing on the use of synchronous satellites for one-way
purposes, such as television.