Abstract: An apparatus for confining an animal within a predetermined area is provided. A loop of electrical wire defining the predetermined area has an AC current from a transmitter passed therethrough. A receiver is tuned to receive a magnetic field generated by the loop and includes circuitry for signalling the animal when the location of the receiver is at a predetermined distance from the electrical wire. The transmitter includes a tuning circuit for reducing the effective impedance of the loop and for potentially eliminating the shape dependence of the loop by capacitively offsetting the inductive reactance portion of the loop impedance.