An SPDT 12V relay switches one circuit between two output paths, while a DPDT 12V relay switches two circuits between two paths each. Both use a 12V control input, but the DPDT configuration can control two separate circuits at the same time.

Compare the relay’s contact configuration, such as SPDT or DPDT, and its rated switching current and voltage with the load’s requirements. Check the rating for the correct load type, since AC and DC contact ratings can differ.

Before installing a 12V relay, check that its control input accepts 12V DC, since some modules support selectable 12- or 24V DC operation. Also confirm whether it activates from a positive or negative trigger, as activation options vary by module.

Some 12V relay modules support selectable 12/24V DC operation, while a 12V-only relay generally should not connect directly to a 24V control system. Check the relay’s input or coil voltage and wiring instructions, and use a 24V-compatible relay or an appropriate interface if needed.