Which type of relay maintains its contact state after the control coil is energized only momentarily?

• A. Latch
• B. Momentary
• C. Magnetic
• D. Reed

Answer: (A)

A latch (latching) relay is designed to remember its last contact position after a brief energizing pulse. It has two stable states: set and reset. When you send a short pulse to establish a state, the contacts stay in that state even after the control coil is de-energized, until you issue the opposite pulse to switch it again. This memory aspect is what makes it ideal when you want a circuit to remain on or off without keeping power applied to the coil. In contrast, a standard momentary relay requires continuous current to hold its contacts in the energized state, and magnetic or reed relays describe the actuation mechanism or a different type of switch, not the memory behavior. The defining idea here is that the latch stores its state until explicitly changed.