| 摘要 |
PURPOSE:To use the lowest bit for a transmission of a transmittable signal in a switchboard by fixing forcibly a specified bit in each channel existing in a specified multichannel frame, to a prescribed value, and sending it out to a digital switchboard side. CONSTITUTION:A data signal from a network 14 is converted to a speed on a transmission line by a shift register 34 of a data speed converting circuit 32 and a data speed converting circuit 33, multiplexed by a multiplexing circuit 40 and sent out to a digital trunk line 22. On the other hand, a multichannel frame received by the trunk line 22 is separated and converted by the multiplexing circuit 40, a distributed to the circuits 32, 33 and signal level converting circuits 38, 39. Subsequently, a receiving data signal is inputted to a shift register 35 by a prescribed timing, and it is set to a shift register 36 and sent to the network 14, but in this case, as for the lowest bit of the register 36, a data 5 of the register 35 does not exist, and '1' is set fixedly. In this way, since the lowest bit of a data is changed to a fixed value, it can be used for a transmission of a transmittable signal.
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