Single Pole Double Throw
A two-position switch or relay contact where the common pin is connected to the NO pin when the switch is not activated, and to the NC pin when the switch is activated.
Also known as a Form C contact or a three-way switch (US) or two-way switch (UK).
Other common switch contact arrangements are the SPST (single-pole, single-throw - a regular light switch) and DPDT (double-pole, double throw - a reversing switch).
Switch - Wikipedia lists examples of numerous switch types.
A two-position switch or relay contact where the common pin is connected to the NO pin when the switch is not activated, and to the NC pin when the switch is activated.
Also known as a Form C contact or a three-way switch (US) or two-way switch (UK).
Other common switch contact arrangements are the SPST (single-pole, single-throw - a regular light switch) and DPDT (double-pole, double throw - a reversing switch).
Switch - Wikipedia lists examples of numerous switch types.