Type N carrier telephone deviation regulator

THE TYPE N system, introduced into the field some 3 years ago for short-haul toll telephone service, provides flat regulation for the group of 12 channels at each repeater and the receiving terminal, and individual channel regulation at the terminal only. Up to about 150 miles this regulation has been ample. Although the flat regulation is adequate beyond that length, the transmission variations caused by temperature changes may exceed the regulating ability of the individual channels. To prevent this condition a deviation regulator has been designed for insertion into the high-frequency line at appropriate intervals. Systems long enough to require a regulator have certain transmission advantages when using a recently developed channel 13 so that the regulator is activated by the 12 channel carriers, 2 to 13. The regulator determines the departures for each channel carrier from its nominal, and regulates the line transmission by networks so as to produce a minimum residual. The regulator is shown schematically in Figure 1. It connects to the output of a low-high repeater, and consists of four main blocks as indicated by the dotted lines: the thermistor controlled shaping networks, the regulator amplifier, the channel filter bank, and the computer and four control circuits.