POWER MANAGEMENT FOR LINE POWERED TELECOMMUNICATION APPARATUS

摘要

Where apparatus connected to a communications line is powered directly from that line it is essential that the current drawn is minimised. The present invention provides a variable power supply comprising a dc to dc conversion circuit (3) controlled by an oscillator (2). The output of the dc to dc conversion circuit (3) is used to power tone detection circuit (4) which monitors for a wake-up tone. On receipt of an appropriate wake-up tone the tone detection circuit (4) provides an interrupt signal to a microprocessor (1) which causes an increase in the oscillator frequency. The increased frequency oscillator (2) increases the power drawn from line via the dc to dc conversion circuit.