초록 ▼

A data communication system which includes a plurality of terminals and a data bus, wherein each of the terminals has autonomous access to the data bus. Normally, all terminals are enabled to receive messages on the data bus. To prevent the simultaneous transmission of messages by two or more termin

A data communication system which includes a plurality of terminals and a data bus, wherein each of the terminals has autonomous access to the data bus. Normally, all terminals are enabled to receive messages on the data bus. To prevent the simultaneous transmission of messages by two or more terminals, each terminal continuously monitors the data bus and is enabled to transmit a message only when the data bus has been silent, e.g., there is an absence of messages on the data bus, for a predetermined period of time which is unique to the terminal, and when a periodic transmission interval for the terminal has been reinitiated. The periodic transmission interval is substantially the same for all terminals, and is measured at each terminal from the time of a previous message transmission thereby. Each terminal includes provision for transferring data in the messages received thereby to an associated utilization device, provided that the data is identified with a proper label, and for converting data transferred from the utilization device into an appropriate message for transmission on the data bus. Preferably, the data bus comprises a twisted pair of wires having short-circuit terminations, with each terminal being inductively coupled thereto, and with the messages being in the form of serial, digital words.

대표청구항 ▼

A method which permits each of a plurality of terminals to autonomously transmit messages on a data communication medium asynchronously with respect to any other of said plurality of terminals, said method comprising the steps, at each said terminal, of: detecting the absence of messages on said dat

A method which permits each of a plurality of terminals to autonomously transmit messages on a data communication medium asynchronously with respect to any other of said plurality of terminals, said method comprising the steps, at each said terminal, of: detecting the absence of messages on said data communication medium; and enabling transmission of a message by said terminal only upon the occurrence of an absence of messages on said data communication medium whose duration substantially equals that of an inter-message gap unique to said terminal, and, the elapse of a transmission interval from a previous transmission of a message by said terminal, said transmission interval having a predetermined duration which is substantially the same for each said terminal.