Electrical power control systems

Abstract

A power control system for the remote control of one or more remote power supply circuits in which a power controller which comprises means for producing an a.c. control signal which is arranged to be transmitted over a single pair of control conductors forming a part of a d.c. isolated control link to remote power supply circuit for the operation thereof, in which variable impedance switching means at the remote power supply circuit modifies the impedance reflected back over the control link to the power controller in accordance with the condition of the power supply switching circuit and in which detector means in the power controller senses changes in the impedance of the variable impedance switching circuit and accordingly provides an indication of the state of the remote power supply circuit.

Dependencies are inferred from the claim text.