Communication interface system for half duplex digital radios

Details Communication interface system for half duplex digital radios Communication interface system for half duplex digital radios

1997-11-03

2000-08-29

Patel, Ajit

Multiplex communications

Duplex

370296, H04L 514, H04L 516

Patent

active

061118605

ABSTRACT:
There is disclosed a voice/data protocol for use with half duplex digital radios. The protocol modifies the X.21 HDLC protocol which is widely employed in the transmission of data for digital radios. The X.21 protocol utilizes a control "C" and an indicate "I" signal. In the steady state in conventional systems, both the C and the I leads are "off". When either a DTE or DCE requires service, the units set their C lead to the "on" condition. The opposite end detects the request for service on the I lead and when communications occur, sets the C lead to the "on" condition. When both the DTE and DCE have send and detected "on" conditions on their C and I leads the circuit transfers to the data transfer state and is ready to proceed to data synchronization. In the present protocol, the C signal is defined as a push-to-talk transmit request to the radio. The I signal is defined as a radio busy. When the I signal is asserted by the radio, the radio is busy transmitting voice, receiving voice or receiving data. Under all cases, when the I signal is asserted, any transmit data function being requested or in progress is terminated. The HDLC data stream is evaluated in conjunction with the new C and I signals to provide data/voice discrimination and a data start/end synchronization.

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