| 摘要 |
In a pulse code modulation transmission system in which voice information is coded and transmitted on message digit spaces and signaling information is digitally transmitted on signaling digit spaces in sequence with the message digit spaces, two-state present condition unidigit on-hook and off-hook signaling information and multistate multidigit signaling information as, for example, address signaling, are combined for transmission in a single signaling bit space by forming a digit-by-digit modulo-2 sum between a binary representation of the two-state signaling information and each bit in the multistate signaling words. The resultant sum is transmitted bit-by-bit in a single signaling digit space in sequence with each group of pulse code modulation coded message digits. At the receiver, the transmitted multistate signaling information is recovered by forming a modulo-2 sum between the successively received signaling bits and a present condition bit stored at the receiver. The present condition bit stored at the receiver is updated when the modulo-2 summation at the receiver generates a unique sequence of binary digits from which a transition in the two-state signaling information at the transmitter can be detected. |
