A rocker switch has a rocking lever type of actuator that makes or breaks the circuit contact when its position is changed. A momentary switch, sometimes called a spring return switch, automatically returns to the rest position. For the (On)/Off/(On) switch, the momentary position is (ON), which is denoted using parenthesis. Single pole, double throw (SPDT) is a three terminal switch that controls two single-wire circuits, permitting only one circuit to be energized at a time. It is commonly used in pairs and sometimes called a three-way switch.