Abstract: A communications system permits animal carried transponders, such as ear tag transponders, to be selectively addressed and detected when an animal is proximate to an unterminated wire. Addresses impressed on a frequency carrier on the unterminated wire are coupled to an animal's transponder using a near field coupling, such as an electrical field coupling. When an animal's address is detected, the animal's transponder responds with a data stream carrying a tone or with a signal of different frequency coupled to the unterminated wire. Coupling is enhanced by connecting signals to be transmitted and a receiver for signals to be received to the animal's body. The unterminated wire can be positioned along a feeding/water trough in an agricultural environment to detect when a particular animal feeds or around a gate to detect when an animal passes through the gate.