Data transmission systems

摘要

A data transmission system comprises a transmitter transmitting data messages to n receivers by means of a link. Each message is preceded by a preamble. Each preamble is such that it can either be recognized only by one of the receivers (to whom, alone, the message is directed) or it can be recognized by all receivers when the message is intended for all of them. Each preamble is recognized if at least x of its y bits are recognized. At each receiver, the received preamble is sampled at a multiple of the bit rate and the respective pulse trains produced by the same-numbered samples in each bit period are individually compared with the two predetermined preambles to be recognized by that receiver. The identities of the pulse trains which match either of the predetermined preambles are recorded and the clock in the receiver is then phase-shifted so as to center its bit periods with the sampling pulses producing that one of the matching pulse trains whose sampling pulses are time-positioned midway of the sampling pulses producing all the matching pulse trains. The sampling rate is then reduced to bit rate, and the receiver is thus synchronized with the bit rate of the incoming message.