TELECOMMUNICATIONS EQUIPMENT-NAMELY, SINGLE FREQUENCY INBAND SIGNALING SYSTEMS COMPRISING OSCILLATOR/DETECTOR UNITS, SIGNAL CONVERTORS, AND TERMINATING SETS; DC SIGNAL CONVERTING UNITS; LINE TERMINATING EQUIPMENT COMPRISING LINE AMPLIFIERS, OSCILLATOR/DETECTOR UNITS SIGNAL APPLIQUE UNITS AND TERMINATING SETS; LINE AND SPECIAL PURPOSE AMPLIFIERS; ECHO CONTROL ECHO SUPPRESSORS AND REPEATERS AND DELAY EQUALIZERS; MICROWAVE TRANSMITTERS AND RECEIVERS, WAVE GUIDE ATTENUATORS AND REPEATERS; PRIVATE LINE EQUIPMENT-NAMELY, ORIGINATING, AMPLIFYING, CONDITIONING, TIMING, TERMINATING, AND INTERFACING UNITS; MULTI-FREQUENCY EQUIPMENT-NAMELY, REMOTE RECALL UNITS AND ADAPTER-INTERCOM UNITS; FREQUENCY SHIFT KEYING UNITS; CARRIER DETECTOR, MODULATOR AND DEMODULATOR UNITS FOR DIGITIZED DATA AND VOICE SIGNALS; PULSE CODE MODULATED CARRIER SYSTEMS-NAMELY, CHANNEL BANKS, REPEATERS, AND SPAN LINES TIE TRUNKS; AUTOMATIC NUMBERING IDENTIFICATION AND TRAFFIC DATA RECORDERS; SUPERVISORY CONTROL AND DATA ACQUISITION SYSTEMS-NAMELY, MICROCOMPUTER DATA ACQUSITION UNITS; TELECOMMUNICATION SWITCHING SYSTEMS-NAMELY, PRIVATE BRANCH EXCHANGES, AUTOMATIC CALL DISTRIBUTORS, COMMAND AND CONTROL STORED PROGRAM BASED SWITCHING CONTROLLERS AND NETWORKS, REMOTE SWITCHING UNITS; MULTIPLEXERS AND DEMULTIPLEXERS; TELECOMMUNICATIONS UNIT ASSEMBLIES TO CUSTOMER ORDER; PRINTED CIRCUIT BOARDS; POWER SUPPLIES; AND MOUNTING, TESTING AND MAINTENANCE COMPONENTS FOR THE FOREGOING