This operates automatically via a transponder that can be carried in the pocket or handbag.
The transponder transmits this coded signal using the tuned circuit.
When the driver grabs the door handle a sensor receives a signal from a transponder in the fob, and unlocks the door.
Next, some sharks are outfitted with a ‘pinger,’ a transponder that emits a signal once a minute.
An unidentified pilot could be no more than a private aviator who unknowingly sends out a wrong signal on his transponder .
The satellite will also return images of earth, and serve as a radio transponder .
A transponder on the windshield automatically deducts the fare when a vehicle passes, with a 50 per cent discount for a car with three or more persons.
They captured these recruits as they left the hive, attached a radar transponder to them and then tracked their flight paths using harmonic radar.
The agency says there is no need at present to dispatch a radio transponder to the asteroid, but adds that it will be keeping a close eye on the rock's progress through the solar system.
His transponder 's signal had been coming from a cave in the nearby volcano.