Abstract: A perforated tape reading mechanism provides a programmable timing function. A drum rotatable by a synchronous motor carries the tape, and is supplied with a ratchet mechanism which permits the drum to rotate by said motor over a partial rotation and then returns the drum for another such cycle through a selectively variable number of ratcheted steps. A tape reader mechanism senses the perforations.

Abstract: An audio amplifier system is provided comprising a variable gain amplifier adapted to receive an input signal, means for detecting periods when the input signal falls below a predetermined level, and sound transducer means arranged to provide a signal proportional to the sound level in the area or part thereof covered by the system for controlling the gain of the amplifier. An inhibitor is provided which is arranged to be controlled by the detecting means so as to prevent any change of the gain of the variable gain amplifier except during periods when the input signal falls below the said predetermined level.

Abstract: An audio amplifier system is provided comprising a variable gain amplifier adapted to receive an input signal, means for detecting periods when the input signal falls below a predetermined level, and sound transducer means arranged to provide a signal proportional to the sound level in the area or part thereof covered by the system for controlling the gain of the amplifier. An inhibitor is provided which is arranged to be controlled by the detecting means so as to prevent any change of the gain of the variable gain amplifier except during periods when the input signal falls below the said predetermined level.