Abstract: A driver control enable and disable circuit for an asynchronous serial local area data distribution system including a plurality of distributed data processing stations connected to a common bus and utilizing a half-duplex signaling protocol which prevents contention between messages originating from different stations. In order to assure message integrity, only the transmitter of the protocol allowed message is enabled. The signals which control the enabling of this transmitter cause reset of the driver of the previously allowed message on the bus by monitoring the driver current.