Abstract: A signal locating apparatus for locating within a frequency band an input signal of a first frequency, the signal locating apparatus including a signal receiver for receiving the input signal. The signal receiver is characterized by having a relatively narrow bandwidth response of variable center frequency, the signal receiver being capable of generating a detected signal when the center frequency is substantially equal to the first frequency, the signal locating apparatus further including search device for varying the center frequency at a relatively high rate so as to cause the signal receiver to search for the presence of the input signal within a frequency band, the search device being operable in response to generation of the detected signal to stop the search for the presence of the input signal.

Abstract: A remote data transfer system, particularly an identification system for identifying objects such as livestock, pets and containers. An interrogator generates a directional light beam which the operator can direct at a selected animal or package up to 30-14 200 meters away; and a tag transponder carried by the object is activated only on receipt of the light beam, and transmits a coded RF signal. The signal is received by the interrogator which displays the identity of the animal derived from the coded RF signal. In its "receive" mode, the tag transponder requires minimal power, thereby prolonging battery life. A short rise time light pulse (or a pulse sequence) is identified and used to switch power to the transponder. After transmission of the coded RF signal, the transponder returns to a low power draw stand-by state. The tag is also able to transmit real time information, with or without the tag identity data.

Abstract: A discriminating apparatus for discriminating a radiant information signal from a background signal, the discriminating apparatus including a radiation sensing means sensitive to an incident signal comprising both an information signal and a background signal and operative to generate an output sensing signal of a level related to the level of the incident signal, and detector means responsive to the sensing signal to detect an information signal component of the sensing signal from a background signal level component of the sensing signal.