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 Equipment, Comprising 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, Span Lines; Tie Trunks; Automatic Numbering Identification and Traffic Data Recorders; Supervisory Control and Data Acquisition Systems-Namely, Microcomputer Data Acquisition Units; Telecommunication Switching Systems-Namely, Private Branch Exchanges, Automatic Call Distributors, Command and Control Stored Program Based Switching Controllers and Networks, Digital Pulse Code Modulated Switching Controllers and Networks, Remote Switching Units; Multiplexers and Demultiplexers; Telecommunications Unit Assemblies to Customer Order; Printed Circuit Boards; Power Supplies; and Testing and Maintenance Units and Structural Mounting Components for the Foregoing