Abstract: A low-current transceiver, powered by two small low-voltage batteries, for use in wireless headset/phoneset applications, such as hands-free headsets used with cellular telephones. Re-use of current from at least one circuit to provide power to at least one other power-consuming element of the transceiver, along with interrupt-driven control of the current made available to transmit and receive circuits, enables extended battery life (e.g., 120 hours). The headset/phoneset circuits incorporate a technique that draws an extremely low supply current from two low-voltage batteries while providing clear two-way communication over a range of about 3 meters.

Abstract: The invention is a circuit and method for providing an auto-off capability for a wireless transmitter, of a type having an audio plug which mates with the output jack of an audio source. The portable transmitter modulates audio signals from the audio source onto a carrier and transmits them to a receiver. The auto-off capability is provided to prolong battery life and degradation of the transmitter circuit and comprises pinching off a FET when the circuit is in an “off” state. This occurs when a pre-determined threshold in a capacitor is reached by not discharging that capacitor. The capacitor is discharged by dropping an input to a comparator below a pre-determined threshold limit when presented with an audio peak and wherein the drop in value causes the comparator output to discharge the capacitor and causing the FET to supply power to the regulator.