| 摘要 |
PURPOSE:To eliminate an erroneous operation signal, by performing the operation of majority logic for the exchange connection signal taken out for every frame between the exchange and the PCM transmission unit. CONSTITUTION:For the purpose of preventing the malfunction of the signal converting unit, one data bit is taken out from one frame and is input to memory M1 of the error correcting circuit and is subjected to the logical operation temporarily and is transferred to memories M2 and M3 in order. AND and OR among outputs D0, D1 and D2 of respective memories are operated, and operations for data three frames before are performed together, thereby obtaining tertiary majority logic result D=D2.D1+D2.D0+D1.D0. If 5-level majority is operated, the error of two continuous bits can be corrected and this method is very effective. In the example of dial pulses of the exchange, the bit interval of the transmission signal in the PCM-30 type system is 2 msec, and respective error generation probalities are 77 days per 6341 years if it is assumed that the line error rate is 10<-2> bits/sec, and therefore, no error is generated practically. |
