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These switches appear externally similar to single pole, single throw (SPST) switches, but have extra connections which allow a circuit to be controlled from multiple locations. Toggling the switch disconnects one "traveler" terminal and connects the other. Electrically, a typical "3-way" switch is a single pole, double throw (SPDT) switch. By ...
The above realizes the function: Door motor = Key switch 1 AND Key switch 2 This circuit shows two key switches that security guards might use to activate an electric motor on a bank vault door. When the normally open contacts of both switches close, electricity is able to flow to the motor which opens the door.
When a pair of contacts touch, they can pass an electrical current with a certain contact resistance, dependent on surface structure, surface chemistry and contact time; [2] when the pair is separated by an insulating gap, then the pair does not pass a current. When the contacts touch, the switch is closed; when the contacts are separated, the ...
A rotary switch consists of a spindle or "rotor" that has a contact arm or "spoke" which projects from its surface like a cam. It has an array of terminals, arranged in a circle around the rotor, each of which serves as a contact for the "spoke" through which any one of a number of different electrical circuits can be connected to the rotor ...
In a switch where the contacts remain in one state unless actuated, such as a push-button switch, the contacts can either be normally open (abbreviated "n.o." or "no") until closed by operation of the switch, or normally closed ("n.c." or "nc") [nb 1] and opened by the switch action.
A Piping and Instrumentation Diagram (P&ID) is a detailed diagram in the process industry which shows process equipment together with the instrumentation and control devices.
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multi position switch, in 83a out position 1 83b out position 2 Relay; 85 relay coil - Important if relay coil has flyback diode in parallel 86 relay coil + Important if relay coil has diode in parallel Relay contacts 87 common contact 30/51 87a normally closed contact 87b normally open contact 88 common contact 2 30/51 (relay) 88a