Abstract: A cellular-based electronic house arrest monitoring (EHAM) system (10) electronically monitors parolees, or other personnel, required to remain at a house arrest location (12) or to report in at the house arrest location during certain hours. Monitoring occurs automatically under control of a host computer (50) at a central monitoring location remote from the house arrest location, regardless of whether conventional telephone service is available at the house arrest location. Tamper detect circuitry detects any attempt to tamper with the components of the system. The EHAM system includes an electronic tag (14) worn by the person being monitored that periodically transmits a unique identifying (ID) signal (16). The ID signal is transmitted at low power, and is receivable only over a limited range, e.g., 150 feet. A field monitoring device (FMD) (20) placed within the house arrest location receives the ID signal only if the tag is within range of the receiver, i.e.

Abstract: A transponder device receives a carrier signal from an interrogator unit. This carrier signal, of frequeny F, is rectified by a rectifying circuit in order to generate operating power. Logic/timing circuits derive a clock signal and second carrier signal of frequency F/n from the received carrier signal. This clock signal reads a unique identifying data word from a programmable read only memory (PROM). The data word is encoded and mixed with the carrier signal in a balanced modulator circuit. The output of the balanced modulator is transmitted to the interrogator unit where it is decoded and used as an identifying signal. The identifying signal identifies the particular transponder device from which it originated. The rectifier and balanced modulator circuits are realized from the same diode elements. All electrical circuits of the transponder device are realized on the same monolithic semiconductor chip.