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. Designing the Experiment [Illustration: _Recording equipment used in the experiment._] delay = (θ)/(360) ρ, where ρ is the period of rotation in seconds “Can people converse over an echo-free, four-wire circuit that has delay like that of a synchronous satellite?”—that is one way of putting the question we isolated to study. The next problem was to find a way of setting up this question in the form of an experiment whose results might be interpreted as a meaningful answer. The problem of apparatus, fortunately, was fairly simple. Two telephone sets in separate rooms were connected by four wires, with one pair going directly from each transmitter to the other receiver, so that no echo would go back the way it came. This gave us the “echo-free, four-wire circuit” we wanted. To simulate the satellite, I inserted a magnetic delay device (_see sketch_) between one of the transmitters and the other receiver. This had a revolving drum on which speech could be recorded and then played back a short interval later. By moving the playback head, I could produce any amount of delay up to two satellite bounces’ worth. At this point, the equipment was ready, but there were still two major problems: (1) how to get people to converse over the circuit in a natural way, and (2) what to observe and measure that would give us an answer to our question.