DATA COMMUNICATIONS TEST EQUIPMENT-NAMELY, EQUALIZERS, AMPLITUDE RESPONSE AND DELAY MEASURING SYSTEMS, AMPLITUDE RESPONSE AND DELAY TRANSMISSION SETS, MULTI-PURPOSE DATA LINE TEST INSTRUMENTS, TRANSMISSION LINE TEST SYSTEMS, TRANSMISSION MEASURING SETS, VOICE AND PROGRAM CHANNEL CABLE CIRCUIT ANALYZERS, MAIN FRAMES FOR ENCASING THE FOREGOING, TEST CONSOLES, CARRYING CASES, RACK ADAPTORS, AND GRATICULE OVERLAY KITS