Abstract: A microprocessor based transmitter and a microprocessor based receiver in which a user interface is located on the receiver. The transmitter has an internal DC digital voltage measuring circuit to determine the voltage level of the battery powering the transmitter. Periodically, the transmitter's microprocessor inserts this digitally encoded voltage level in the sub-code area of the digital data being transmitted. The receiver decodes the DC voltage level of the transmitter battery, displays it, and inserts this voltage level in the sub-code area of its digital audio output signal. The voltage level of the transmitter battery is automatically recorded in the sub-code area of the DAT. By observing the DC voltage level, a trained operator can determine when the batteries are nearing the end of their useable life or that the battery voltage level is approaching its cut-off level.