L-4 System: Basic and regulating repeaters

The line repeaters of the L-4 system represent a hierarchy of repeaters of increasing complexity: basic, regulating, and equalizing repeaters. Based on a building block philosophy, each of the more complex repeaters performs all of the functions of the less complex types plus additional functions of its own. The simplest, the basic repeater, is a plug-in unit with a shaped gain-frequency characteristic that compensates for the transmission loss of two miles of cable. The regulating repeater includes all of the components of the basic repeater plus two dynamic gain-regulating circuits and a deviation equalizer. Both repeaters include line building-out networks to compensate for departures from the nominal two-mile spacing. This paper develops the building block philosophy of the line repeaters and considers those aspects of the basic and regulating repeaters that contribute to load carrying capacity, reliability, noise figure, and modulation performance. It emphasizes the design features of the line repeaters that contribute to a fully-hardened system.