Abstract: In a digital communications system for transmitting and receiving digital data over a CSMA-type network having a source for transmitting a source signal comprising a synchronization interval and a data interval and at least one receiver for receiving a second signal having a second synchronization interval and a second data interval corresponding to the data interval of the source signal, comprising: receiver means responsive to the source signal for synchronizing the source within the synchronization interval and providing a retransmit request signal indicative of the source signal; transmitter means responsive to the retransmit request signal for synchronizing at least one receiver within one CSMA time interval delay of the synchronization interval and for transmitting the second data interval to the at least one receiver within one CSMA time interval delay of the source data interval; and interface means for synchronizing the receiver means with the transmitter means to enable data transmission therebetwee

Abstract: The inherent structure of redundant information fields contained in the message format of a multifrequency communication system is utilized to determine if the information on the individual hops has been degraded due to interference. By detecting bit errors in the received data sequence and identifying the frequencies on which signals representing the bits in error were transmitted, one can block out data from those frequencies on a dynamic basis. The received data sequence is correlated against the possible code words that might have been transmitted. The result of this correlation is a decision by the receiver that a particular code word was transmitted. Then, the code word that the receiver decides was transmitted is compared against the received data sequence and bit errors are identified. Finally, by knowing the relationship between the transmission frequencies and the order of the received bits, the receiver can identify the frequencies on which signals representing the bits in error were transmitted.