Electronics abbreviation	British mains wiring name	American mains wiring name	Description	Symbol	IEC/ 60617
SPST or Single pole, single throw	One way	Two way	A simple on-off switch: The two terminals are either connected together or not connected to anything. An example is a light switch.
SPDT or Single pole, double throw	Two way	Three way	A simple changeover switch: C (Common) is connected to L1 or to L2.
SPCO or Single pole changeover or Single pole, centre off			Equivalent to SPDT. Some suppliers use SPCO for switches with a stable off position in the centre and SPDT for those without.
DPST or Double pole, single throw	Double pole	Double pole	Equivalent to two SPST switches controlled by a single mechanism.
DPDT or Double pole, double throw			Equivalent to two SPDT switches controlled by a single mechanism: A is connected to B and D to E, or B is connected to C and E to F.
DPCO or Double pole changeover or Double pole, centre off			Equivalent to DPDT. Some suppliers use DPCO for switches with a stable off position in the centre and DPDT for those without.
	Intermediate switch	4-way switch	DPDT switch internally wired for polarity-reversal applications: only four rather than six wires are brought outside the switch housing; with the above, B is connected to F and C to E; hence A is connected to B and D to C, or A is connected to C and D to B.