US Patent 7725138 Apparatus for control of in-battery module

An apparatus (100) is provided for powering an in-battery electronic application module (118) without the use of an external on/off switch. A battery pack (102) is electrically coupled to a radio (104) via three interface contacts: power (108), ground (112) and single-wire serial data port (110). Circuitry is included within the battery pack (102) to sense and monitor data activity on the single-wire serial data port (110) generated as the radio (104) is turned on. Based on the level and timing (200) of the data activity present on the single-wire serial port (110), the electronic application module (118) can automatically be turned on (208), remain on (210) and turned off (212).