Abstract: An apparatus and method are provided for use in tracing a cable; the apparatus and method allows a cable to be identified at any point along its length. The apparatus includes a transmitter for applying a unique waveform to a cable of interest, a line terminator for forming a cable loop through which current can flow, and a detector which is capable of detecting both voltage (electric field) and current (magnetic field). The unique waveform induces both a magnetic and an electric field in specifically identifiable patterns.

Abstract: An electronic thermostat utilizing a switched power supply which operates either from a voltage appearing across an open circuit at a heater or air conditioner activation circuit (de-energized state) or from a current flowing in the activation circuit upon short circuiting (energized state) of the activation circuit. The power supply provides an uninterrupted source of power to the electronic thermostat which controls the source of input power to the power supply in addition to the state of the activation circuit. The electronic circuit implements a piecewise linear, with hysteresis loop discontinuity, control function.