Abstract: An automatic gain repeater for varying the amplification of AC signals transmitted through a telephone subscriber loop in accordance with the impedance of such subscriber loop is described. The automatic gain control circuitry includes controllable variable gain amplifiers connected in series circuit arrangement with the subscriber loop. The gain of the amplifiers is varied, in a continuous manner, in accordance with the subscriber loop line impedance such that the overall transmission line loss is a constant predetermined value. Gain of the amplifiers is accomplished by means of a control signal generated in a loop extender circuit that is coupled to the subscriber loop.Impedance networks coupled to gain repeater hybrid transformers provide minimum operating power loss with maximum power transfer between the automatic gain repeater circuit and subscriber loop while maintaining adequate transhybrid loss between the two directions of transmission and matching input impedance.

Abstract: There is described a remote switching terminal which functions as a concentrator switching stage for a central office switching system, such as a standard No. 5 crossbar switch. The remote station connects subscriber phones directly into the horizontal lines of the crossbar, which are fewer in number than the subscriber lines that normally tie into the vertical lines of the crossbar. Control of the remote station is by a microprocessor which communicates over a data link to a microprocessor at the central office. Cross connections are duplicated at the remote station so as not to interfere physically or electrically with the operation of the central office equipment.

Abstract: A delta modulator produces a digital bit stream from an input analog waveform and applies same to bit-averaging circuitry dividing the bit stream into time-frame intervals and computing the average slope per frame. Each average time-frame slope value is transmitted over a communication system as a discrete digital signal and at a receiver each such signal is employed to set the gain of a multi-level integrator and thus incrementally reconstruct the original waveform.