Abstract: The present apparatus for controlling the application of telephone line power in a telephone set has obviated the requirement for a local source of power at the premises of a telephone customer. A data processor-based telephone set incorporating the present invention comprises a power supply having first and second voltage storage devices (C401, C402) which accumulate charge from the telephone line. First and second regulator circuits (410, 420) regulate the charging of the voltage storage devices and the power distribution to power-consumptive components of the telephone set during on-hook and off-hook switchhook conditions. A voltage threshold detector (301) actuates a power-down of power consumptive components including the data processor (210) when the power supply voltage falls below a particular threshold value. In the meantime, power is continuously provided to certain essential components such as the volatile memory (220) of the data processor.