How does the spoiler actuation mechanism work on the Airbus A340?
Most aircraft utilize a weight on wheels switch. When the landing strut is compressed when ground contact is made, the weight on wheels switch is activated. The signal is distributed to various systems in the aircraft, including the spoiler system.
The spoiler is activated as soon as the aircraft touches the ground to "scrub off" any lift and to make sure the aircraft doesn't become airborne as the jet engines spool down.