Audio teaching installation for several classrooms - has central console with main oscillator to synchronise signals to pupils

摘要

The audio teaching machine has a centrally situated steromicrophone connected to an amplifier, controlled by an oscillator (74) which transmits at a common carrier frequency of about 150 HKz. This is used to synchronise the transmissions to a number of classrooms, which may be on different frequency channels or the same channel. If similar frequencies are used to two classrooms they require to be separated by a space at least equal to that of one classroom. - Each classroom is equipped with its own transmitter (56-61) synchronised to the main oscillator. The pupils each have their own receiver or headphones (68-73).