| abstract |
A system for passively identifying remote objects such as livestock. A power transmitter (2) transmits a plurality of radio frequency burst signals at a given frequency, and a uniquely coded transponder (8) associated with the object to be identified produces a plurality of coded identification signals in response to the burst signals from the transmitter. The coded identification signals are read by a receiver (14) to identify the object. The transmitter and receiver are time division multiplexed (16, 30 & 32) for alternate operation. Accordingly, when an object is to be identified, the transmitter (2) is switched on to transmit the burst signals, thereby activating the transponder (8) to produce the coded identification signals. The transmitter (2) is then switched off and the receiver (14) switched on to receive the identification signals for identifying the object. The on/off operation takes place at a speed of 20,000 times per second. |