Transponders were originally developed to be attached to objects which needed to be located, and are still used in this manner today. A transponder functions by receiving a signal, called an "interrogator" because it is effectively "asking" for information, then automatically conveying a radio wave at a predetermined frequency.

In order to broadcast a signal on a different frequency than the one received, a frequency converter is built in. By receiving and transmitting on different frequencies, the interrogator and transponder signals can be detected simultaneously, thus providing a unique code.

In short, a pet MicroChip is installed at a point between the shoulder blades or scapula and provides a unique code which is recorded with the information being stored in a national database which is run by pet-detect, a subsidiary of the Kennel Club.

If your pet is lost or stolen it has a far greater chance of being found if you have a MicroChip installed in your pet.