Abstract: Word synchronization of a digital message comprised of spaced predetermined synchronizing words is indicated by a first initial detection of a synchronizing word followed by detection of two synchronizing words out of the next four synchronizing words.

Abstract: An audio muting device for use in a transceiver which receives digital data preceded by a dotting pattern uses a detection/decoder for detecting the non-audible dotting pattern and a controller for actuating a muting switch whenever the dotting pattern is detected.

Abstract: A channel busy arrangement for use in a radio-based data transmission system comprising a plurality of data terminals. A carrier activity signal (CAS) generated by a receiver associated with a data terminal is used to trigger a CAS pulse of approximately 300 msec. A demodulated audio signal from the receiver is coupled to a SYNC detector for detecting a data synchronizing (SYNC) signal generally transmitted before a data message and to an optional continuous tone coded squelch system (CTCSS) for generating a CTCSS signal. The CAS pulse, SYNC signal and CTCSS signal are logic ORed to generate a channel busy signal used for inhibiting data transmission. Thus, data transmission is inhibited only during a 300 msec CAS pulse, when a SYNC signal is present, or during valid non-data transmissions (voice) even in the presence of an interfering signal.

Abstract: In a radio communication system having a command or base station and one or more controlled stations, the base station transmits outbound binary function messages to the controlled stations in order to make an inquiry or give a command to one or all of the controlled stations. The controlled station responds with an inbound binary message. The outbound messages comprise a sequence of binary bits at a first rate and having a first synchronizing word of nine bits, a first address word having eight message bits and four parity bits and produced three times, a second synchronizing word that is the binary inversion of the first synchronizing word, a second address word having eight message bits and four parity bits and produced three times, a third synchronizing word that is the binary inversion of the first synchronizing word, and a command word having eight message bits and four parity bits and produced three times.

Abstract: In a radio communication system having a transmitter at a first location for sending binary messages to a receiver at a second location, it is necessary that the receiver be synchronized with the binary message so that the start or beginning of the message can be accurately determined. This synchronization is provided by synchronizing words spaced in each binary message, each synchronizing word having a predetermined sequence of binary values. If a receiver receives two synchronizing words having the predetermined binary values, it produces an in-synchronization signal so that messages will be properly received. If, after the in-synchronization signal is provided, a predetermined consecutive number of synchronizing words failing to have the predetermined sequences are received, then the receiver produces an out-of-synchronization signal. The in-synchronization and out-of-synchronization signals provide reliable operation of receivers which receive binary messages.

Abstract: In a radio communication system having a command or base station and one or more controlled or mobile stations, the base station continuously transmits outbound function messages in binary bit form to the mobile stations. Each outbound function message comprises a sequence of binary bits forming a first synchronizing word, a first address word transmitted three times, a second inverted synchronizing word, a second address word transmitted three times, a third inverted synchronizing word, and a command word transmitted three times. All mobile stations receive the outbound messages and synchronize on them, but only that mobile station whose address is transmitted responds. Each mobile station is synchronized when it properly receives two consecutive synchronizing words in sequence, and remains in synchronization unless five consecutive synchronizing word errors occur. The response from the mobile station to the base station is an inbound message also in binary bit form.