Abstract: A circuit for use in a p.w.m. type power supply for increasing the efficiency thereof when the supply operates at low power levels. The circuit increases the efficiency by eliminating in a predetermined manner some of the p.w.m. pulses used to drive the power switching means of the supply.

Abstract: A plural channel amplitude modulated telephone carrier system having a plurality of transmitters to provide for the transmission of a like plurality of frequency division multiplexed, amplitude modulated carrier signals in a common direction along a transmission line to a remote termination of the transmission line, and an automatic carrier level coordination control circuit having a first circuit means for developing a d.c. control signal that varies as a predetermined function of the transmission line length, and a second circuit means connected to the first circuit means for controlling the transmit power of each of the aforesaid carrier signals as a function of its own carrier frequency and as a function of the d.c. control signal. The telephone carrier system may be of the station carrier type and may have two or more plural channel amplitude modulated carrier sub-systems, each having its own transmission line.