Abstract: A communication switch circuit is provided by which quasi-duplex communication may be had between a telephone party and a mobile unit in a simplex two-way radio communication system. Specifically, the communication switch circuit includes (i) a keying circuit to selectively energize a transmitter and (ii) an interrupt circuit to intermittently, temporarily deenergize the transmitter to permit reception from a mobile unit. The communication switch circuit further includes a control circuit which prevents reenergizing of the transmitter if a signal is received from a mobile unit while the transmitter is temporarily deenergized thereby permitting a mobile unit to interrupt the telephone party and interject a comment. The communication switch circuit also includes control circuits which permit a mobile unit to initiate and terminate calls.