Some electronic switching circuits

SWITCHING usually is considered as the physical opening or closing of metallic circuits as, for example, where a circuit breaker or a knife switch is put in motion mechanically to break or make connections between conductors leading to a circuit or device. However, switching may be performed in other ways, as by changing the operating potentials from one polarity or magnitude to another polarity or another magnitude. For example, a control voltage on an amplifier tube may be altered to change the circuit from a nonamplifying to an amplifying condition. The making of circuits operative or inoperative by a change in polarity or magnitude, or both, as performed by means of an electronic device is called “electronic switching.” No moving parts are involved and the control may be much faster and more economical than control by mechanically operated devices. If two circuits or devices are controlled by an electronic switch, it is called a two-circuit electronic switch.^1,2 In the same way, if three, four, or five circuits are controlled, the electronic switch is called a three-, four-, or five-circuit electronic switch.