POWER FEED CIRCUIT PROVIDING BOTH ON-HOOK AND OFF-HOOK POWER FOR TELEPHONE SUBSCRIBER LOOP

摘要

A power feed circuit provides power for a telephone subscriber loop connected to a unit of terminal equipment. The power feed circuit includes a first current supply circuit for supplying power to the subscriber loop when the unit of terminal equipment is in an on-hook condition and when the unit of terminal equipment is in an off-hook condition, and a second current supply circuit for supplying power to the subscriber loop only when the unit of terminal equipment is in the off-hook condition. Each current supply circuit includes a respective battery, transistor and bias network. The first current supply circuit is connected to the subscriber loop via a diode which is reverse-biased when the unit of terminal equipment is in the on-hook condition. The power feed circuit may be usefully applied in an Optical Network Unit (ONU) of a"fiber-in-the- loop" telephone system or in a Subscriber-Cable Interface Unit (SCIU) of a cable telephony system.