—_ 4-39 distribution stations served experimenters in locations at both atolls, including five shipboard stations operated by the rediosignal system for the underwater shots. These stations are listed in Table 1. To provide greater flexibility, the basic timing sys*’7 was completely revised for this operation. By means of @ pat:::.- board on the sequence timer, as many as twenty-four separate times could be selected at any half-minute interval from -60 minutes to -2 minutes. and at any nalf-second interval from -2 minutes to # 1 seconc. Tne selected times were transmitted to the timing station over a single pair of wires as a series af 100-millisecond pulses. Another patch-board on the timing station decoder provided the means whereby any of the timing signals received from the Control Point could be selected and distributed to any number of users. Two radio-tone timing signal systems supplemented the hardwire systems at Eniwetok and Bikini by providing signals to users in locations where hardwire signals were not feasible. Separate radio-tone systems operated the major instrumentation on the two underwater shots and on the high-altitude balloon phot. A similar system was installed at Johnston Island. A firing-tone transmitter furnished the signals for arming and firing the two underwater devices, Users requiring radio signalt were supplied with EG&G Tone-receiver units, consisting of a radio receiver, a tone-sensitive relay system, output relays for operating equipment. and heavy-duty To eliminate the possi- bility of false triggering, two different audio tones were transmitted Simultaneously for each timing signal. «Poel/op que 203 PAGE “7S

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