A push button is a momentary switch that makes contact only while pressed. The symbol shows two terminals with a bridging element held by a spring mechanism. Push buttons are used for doorbells, reset switches, and start/stop controls.
A relay uses an electromagnetic coil to mechanically operate a switch. The coil symbol looks like an inductor (or rectangle) and the contacts are drawn as a separate switch. Relays allow a low-power signal to control a high-power circuit safely.
An SPDT (single-pole double-throw) switch connects one input to one of two possible outputs. The symbol shows a hinged arm that can swing between two contact points. It is commonly used in three-way lighting circuits and signal routing.
An SPST (single-pole single-throw) switch is the simplest switch type with one input and one output. The symbol shows a hinged line that can make or break contact with a terminal point. It is used for basic on/off control in circuits.
