| 摘要 |
PURPOSE:To prevent the spread of a transmission band and the mixing of a synchronizing signal component to the voice band by using a memory element such as a RAM as a variable delay circuit so as to change the write/read clock frequency periodically and applying scramble processing to the voice signal. CONSTITUTION:A signal is sampled by an output of a clock frequency control circuit 6 at the transmission side and scramble processing is applied by revising a clock frequency f1(t) at write to the RAM 3 and a clock frequency f2(t) at read from, the RAM 3, and the clock frequency control circuit 16 at the reception side uses the clock frequency f2(t) for write to the RAM 13 and the signal is decoded by the read at the clock frequency f1(t). The frequencies f1(t), f2(t) are changed by the period being the sum of the delay time at the RAMs 3, 13 at the transmission/reception side.
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