Switches

A switch is a component that makes or breaks an electrical circuit, controlling the flow of current. In its simplest form it has two states, open and closed, and is operated by mechanical action such as pressing, sliding or rotating. Switches are described by the number of separate circuits they control (poles) and the number of positions each pole can connect (throws); a single-pole single-throw switch is the most basic, while multi-pole and multi-throw arrangements handle more complex switching.

Many switch designs exist for different needs. Toggle, rocker, slide, rotary and push-button switches differ in their actuation and feel. Momentary switches return to their rest state when released, while latching switches hold their position. A mercury switch uses a blob of liquid mercury that moves to bridge contacts when the device is tilted, giving a quiet, contactless make. Reed switches, operated by a magnetic field, provide sealed switching without manual contact. Each type is rated for the maximum voltage and current its contacts can handle safely.

A practical issue with mechanical switches is contact bounce. When the contacts close, they do not settle instantly but spring apart and re-close several times over a few milliseconds, producing a burst of rapid transitions. In circuits that merely turn a lamp on this is harmless, but where a switch feeds a counter or logic input it can register as multiple operations. The remedy is debouncing, achieved either with hardware such as resistor–capacitor filters or latches, or with software that ignores further changes for a short time after the first.

Frequently asked questions

What do poles and throws mean?

Poles are the number of separate circuits a switch controls, and throws are the number of positions each pole can connect to.

What is switch bounce?

It is the brief, repeated opening and closing of contacts as they settle when a switch is operated, producing several rapid transitions instead of one clean change.

How is contact bounce dealt with?

By debouncing, using hardware filters or latching circuits, or software that ignores further changes for a short interval after the first transition.