| 摘要 |
918,371. Phase synchronizing devices for secret telegraphy. GRETAG A.G. Sept. 26, 1961 [Sept. 30, 1960], No. 34502/61. Class 40 (3). In a secret telegraphic system of the type in which extra pulses are interleaved in the data pulse train at the transmitter and deleted from the pulse train at the receiver, the insertion and deletion of extra pulses being controlled, for example, by identical punched tapes at the transmitter and receiver which tapes have to be read synchronously at the transmitter and receiver, means are provided to ensure that reading of the two tapes commences simultaneously at the transmitter and receiver, subsequent synchronization being effected by known means not described. At the transmitter 24, Fig. 1, immediately prior to commencing tape reading stepping of a cam 40 by a pawl-and-ratchet mechanism 32, 36 is started and at the same time an attempt is made, by transmitting a signal over a radio link to a receiver 26, to initiate simultaneously the stepping of a similar cam 40 at the receiver. However, owing to noise or fade-out the cam 40 at the receiver may start either before or after the cam 40 at the transmitter and the device described functions to bring these two cams into phase so that at the end of one revolution they can both actuate devices 52 to initiate simultaneously the tape reading. As the cam 40 at the transmitter rotates it causes devices 44, 46, 48, 50 to generate a sequence of characters, e.g. A, B, C, D, which are transmitted to the receiver where they are compared, in a comparator 56, with a similar locally-generated sequence. If the two sequences received by the comparator 56 are in phase agreement, e.g. if the two A's are received simultaneously, then the cams 40 are in phase and no action is required. If, however, the two character sequences are not in phase, e.g. if an A is received with a B then the comparator suitably controls a differential gear 54 so as to bring the two cams into phase. The actual comparison can be done by relays and the correction effected automatically or the two character sequences can be used to control a teleprinter so arranged that printing only occurs when the characters are not in phase and any correction can be effected manually.
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