Which device requires a short pulse to energize a relay?

• A. Latching relay
• B. Pulse width modulation
• C. Digital output
• D. Accumulator

Answer: (A)

A latching relay is designed to change state with a brief energizing pulse and then hold that state without continuous power. The coil’s magnetic action briefly flips a latch, and once the pulse ends, the contacts stay in the new position due to the magnetic memory. This makes short pulses ideal for toggling a relay while saving energy. PWM is a method for controlling average power by rapidly switching on and off; it’s about how you drive a device, not a component that remembers its state. A digital output is just a binary signal that can be high or low and doesn’t inherently lock the relay in a new state after the pulse. An accumulator stores energy or data, not the state of a relay.