What is the NO SPST normally open relay? The NO Normally-Open SPST (Single Pole Single Throw) relay has an opened circuit state when no current is applied to its coil so basically it disconnects the ...

These designations spell out the number of contacts and how they behave during operation. For instance, a basic on/off light switch is an example of a single-pole (i.e., one-circuit) single-throw (i.e ...