Battery powered radio transmission system - saves power by switching off during breaks and by matching transmit power to signal strength

摘要

The free-space transmission system, e.g ultrasound remote control or IR link between headphones and tv receiver, saves power by matching the transmit power to fluctuations in a signal strength and by switching off the system during breaks in transmission. Alternatively, if the transmitter and receiver are not local but relatively far apart so that each is subject to different conditions, an additional signal may be used to control the transmit power according to the strength of the signal received by the receiver. This additional signal may be AM or FM modulated onto the wanted signal.