K24A syncroplex telephone carrier system
01 January 1960
K24A system was developed by the International Telephone and Telegraph Laboratories for the exchange junction circuits, 5 to 20 miles long, with a total attenuation of 200 dB at 500 kc/s. Double-sideband suppressed-carrier amplitude-modulation is used, each channel occupies 8kc/s band and the channel spacing is 16 kc/s, so that 24 channels can be accommodated between 60 and 480 kc/s. Principal required characteristics and system parameters are listed, functions of main equipment units are briefly presented. 32 dB, 60-480 kc/s transistor amplifier with 25 dB negative feedback, channel modems, and other units are described. The system was developed with a particular stress on the simplification of installation and maintenance.