Automatic switching of two sound sources - uses electronic switch and first source is normally connected, while second source is connected when it delivers signal

摘要

In its rest state the switch (K) connects the first signal source (To) to an amplifier, and in its operated state it connects the second signal (TM) source to the amplifier. A sensor for signal detection is permanently connected to the second signal source, and operates the switch when the second source delivers a useful signal. The switching system may be used for cine projectors which may use films with optical or magnetic sound tracks. Normally the optical reading head (To) is used. When the film has a magnetic sound track, the magnetic head (TM) delivers signals and triggers operation of the switch.