Use of a ``secret'' feedback mechanism to the presenter, supplying information about acoustics, delays in response time of the computer demonstration and audience reaction was crucial to the success of the presentation. To the conference participants, the disembodied voice of the presenter appeared to know exactly what was going on in the room, adding to the immediacy of his presentation.
The unix ``talk'' program was a convenient way to do this, since the talk window could exist innocuously on both local and remote displays, and the dialogue was neither seen nor heard by the audience.