Application and transmission features of a new 12-channel open-wire carrier system

A new, miniaturized, 12-channel open-wire carrier system, the Lenkurt 45A system, is described. For use in the 40-to 150-kc frequency region, it co-ordinates fully in level and frequency allocations with present Lenkurt 42C and Western Electric J carrier systems using this frequency space. Because of the inclusion of 2-pilot regulation for flat and slope gain control, supplemented by channel regulation with a range of about ± 7 decibels (db), more stable circuit operation is obtained than in previous open-wire carrier systems. The design which results is much reduced in cost as compared to past systems in this frequency range, and affords an opportunity for considerable expansion in use of open-wire plant above the 35-kc range. This use is further enhanced by optionally supplied compandors, permitting many instances of use of wire lines transposed only for 35-kc operation. An important feature of the system is terminal design and frequency allocation co-ordinated for open-wire, single cable, and radio use. This permits great flexibility in interconnecting among such systems without need for intervening terminals. Miniaturization carried to a high degree results in a terminal occupying but 31 1/2 inches of vertical space on a telephone-type relay rack. Back-to-back operation permits as many as 96 channels in two 11-foot 6-inch bays. Extensive use is made of standardized plug-in units further supplemented by plug-in band filters and signaling options, to fit a wide variety of application requirements.