Terminal Arrangements

The L-4 coaxial line is described in Ref. 1 as a transmission facility with a message capacity of six mastergroups. These six mastergroups are placed on the line in the frequency assignment shown in Fig. 1. Each mastergroup starts as a U600 basic mastergroup, formed by L-type multiplex ( L M X ) frequency-division multiplex equipment. An important function of the L-4 terminal equipment is the translation to line-frequency assignment of the six mastergroups. Earlier mastergroup multiplexing equipment, designed for the L-3 coaxial cable system and later used for TH microwave radio systems, has a capacity of three mastergroups. The U600 basic mastergroup consists of 600 single-sideband channels stacked up in the frequency range 564-3084 kHz in 12-channel groups and 60-channel supergroups by frequency division multiplex techniques, using L M X equipment.2 This frequency assignment is now 993 994 THE BELL SYSTEM TECHNICAL JOURNAL, APRIL 1969 MHZ -17.548 18.112 MHZ MASTERGROUP 6 - 15.028 ~ 14.412