Abstract: An estrus detection system using a transponder mounted to an animal and including a motion sensor. The motion sensor produces a series of pulses as a function of movement. A counting circuit is energized by the sensor. A storage circuit retains the count together with an identification code unique to the animal. The transponder is interrogated to receive data and such is processed to determine estrus.

Abstract: A system for passively identifying remote objects such as livestock is disclosed. A power transmitter transmits a plurality of radio frequency burst signals at a given frequency, and a uniquely coded transponder 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 to identify the object. The transmitter and receiver are time division multiplexed for alternate operation. Accordingly, when an object is to be identified, the transmitter is switched on to transmit the burst signals, thereby activating the transponder to produce the coded identification signals. The transmitter is then switched off and the receiver switched on to receive the identification signals for identifying the object.