21 Communication Equipment-Namely, High and Low Frequency Amplifiers, Antennas and Supporting Masts, Television Receivers [ and Transmitters] , Solid State Semiconductor Devices, Microwave Components, [ Television Amplifiers, Television Converters, Television Modulaters, Television Level Monitoring and Audio Level Monitoring Equipment, ] Command Signal Generation Equipment, Command Decoding Equipment, [ Pole Box Assemblies, ] and Electronic Controls for Machinery and Industrial Processes and Power Supplies