analog, digital or hybrid electrical equipment; namely, electrical audio amplification devices for the purpose of limiting the modulation of transmitters and magnetic sound tracks, commonly known as limiters; electrical audio amplifiers which automatically equalize the spectral components of an input signal, commonly known as audio processors; electrical devices which cause a signal transmitted by radio waves to take on a specific modulation characteristic; namely, stereophonic generators for FM transmissions; electrical devices for modulating ultrasonic subsidiary modulation characteristics of FM transmissions, commonly known as SCA or SCMO generators; stereophonic generators for AM transmission; modulation adapters for AM transmitters; monitor and monitor adapters for the measurement of the modulation characteristic of any or all of the above devices; electrical amplifiers which are adapted to interface with a public telephone system so as to enhance the character of a signal passed to the public telephone network so as to make it more desirable when re-broadcast