single pole single throw (switch) (SPST)
A circuit breaker is a switch that establishes or releases an electrical connection via its switching contact. Depending on the design, a distinction is made between on-off switches with one switching contact, referred to as a single-pole on-off switch, or with two switching contacts, referred to as a double-pole on-off switch.
The Anglo-Saxon acronyms for these two designs are Single Pole Single Throw (SPST) and Double Pole Single Throw (DPST) and thus indicate the number of contact paths.
On-off switches are available in single-pole and double-pole versions. Whereas in the single-pole version one switching contact can open or close a connection, in the double-pole version, DPST, there are two switching contacts that are mechanically connected to each other. With such a DPST switch, two connections are always switched or released simultaneously. On-off switches are available with mechanical release, electromechanical and as electronic on-off switches.