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Impulse relays (bistable or latching relays) are used in control panels, distribution boards, and building automation systems where a circuit must be toggled ON or OFF from multiple control points without continuous coil power. Engineers choose them to simplify multi-point lighting control wiring, reduce PLC output load, and latch auxiliary circuits in machine and HVAC panels.
Impulse relays — also called bistable or latching relays — toggle their output state on each control pulse and hold that state with zero coil power. This category includes single-pole (1NO) and double-pole (2NO) versions for switching one or two independent circuits, modular DIN rail types for control panels and distribution boards, and electronic (solid-state) variants for high-cycle applications. Key brands stocked include Schneider Electric (Acti9 iTL), ABB, Siemens (5TT4), Finder (Series 13), Hager, and Legrand.
Typical applications include multi-point lighting control in industrial and commercial buildings, HVAC zone switching, conveyor section latching, load shedding in energy management systems, and auxiliary circuit control in machine panels — anywhere a held output state is needed without continuous coil energization.
| Type | Best for | Typical life |
|---|---|---|
| Electromechanical bistable | Standard panel and lighting control | 100k–300k ops (electrical) |
| Electronic / solid-state | High-cycle or high-frequency switching | Up to 10M+ ops |
| Double-pole (2NO) | Switching two circuits from one pulse | Same as above by type |
A standard relay requires continuous coil power to hold its state. An impulse relay toggles on each pulse and holds the state with no coil power — reducing energy use and control wiring complexity.
Yes, if the PLC output voltage and current match the coil specification. Transistor outputs driving AC coil types may need a buffer relay between the PLC and the impulse relay.
Select a model with an auxiliary status contact wired back to a PLC input, or use a version with a mechanical position indicator window on the housing.
Use AC3-rated contacts for inductive loads such as motors and fan coil units. AC1 ratings apply to resistive loads only and will overstate capacity on inductive circuits.
