Abstract: A radio range finding system includes a radio frequency transmitter adapted to be located adjacent an area in which distance is to be monitored, a transmitting antenna, and a receiver unit. The receiver unit has a multiplicity of radio signal receivers each having a highly directional receiving antenna with the receiving antennae of the multiplicity of receivers having their axes of maximum sensitivity oriented in different directions, and an analyzer for determining a composite of the field strengths of the radio signals received by the receiving antennae, and providing an output indicative of the composite field strength. The receiver may detect when the composite field strength at the receiving antennae fails below predetermined values, and generate a signal at that time. The vector sum of the field strengths of the radio signals are derived from the square root of the sum of the squares of the field strengths of the several signals.

Abstract: An animal restraining system includes a radio frequency transmitter adapted to be located adjacent an area in which the animal is to be restrained, a transmitting antenna, and a collar unit worn by the animal. The collar unit has a multiplicity of radio signal receivers each having a highly directional receiving antenna with the receiving antennae of the multiplicity of receivers having their axes of maximum sensitivity oriented in different directions, and an analyzer for determining a composite of the field strengths of the radio signals received by the receiving antennae, and detecting when the composite field strength at the receiving antennae falls below predetermined values. When the detected composite field strength falls below a first predetermined value, a first warning signal is generated to the animal, and a second and different warning signal is generated when the composite field strength falls below a second predetermined value.

Abstract: A system for training an animal to remain in a predefined area comprising a plurality of distance zones from a central point where the perimeters of the distance zones are measured by the received strength of a radio frequency transmission, comprising a transmitter, a receiver for receiving transmissions, a measurement circuit for establishing a numerical value of the magnitude of a received transmission from the transmitter with respect to each of the zone perimeters, a digital memory for storing numerical values, control logic for converting the magnitude of the received transmission to a numerical value, control logic for comparing the received transmission numerical value with the stored numerical values, an animal control signal generator mounted on the animal for imparting warning sounds and applying physical stimuli, and an actuation circuit responsive to the comparison logic for actuating the signal generator for imparting to produce one or both of the warning sounds or stimuli to the animal dependent