With overcrowded jails and work-release centers and the high cost of keeping an individual incarcerated, systems for electronic supervision of criminals have gained increased attention. Benefits of such systems include relieving overcrowding, avoiding the incarceration of non-violent criminals or persons guilty of less serious crimes with career criminals, and allowing probation or parole officers to keep track of a substantially larger number of incarcerees than in the past. However, such a system must also be cost effective to operate.
Prior art personnel monitoring systems, however, have complex circuits for identifying an incarceree. One such system disclosed in U.S. Pat. No. 4,747,120 to Foley, discloses a system utilizing an automatic dialer which randomly calls various incarcerees assigned to a parole officer. A bracelet, which includes coded information and is worn by the incarceree, is placed in a decoder for identification by a sensor. When the bracelet is inserted into the sensor, the decoder couples itself to the telephone line and uncouples the telephone from the telephone line. The sensor then reads the coded information and the decoder performs a handshake procedure if the coded information is the correct information. Any suitable coding scheme may be used, optical, magnetic, capacitive, etc. In the embodiment of the sensor described therein, the coded information is either a sliver of metallic material or a blank. When the sliver is lined up with a foil spiral of an oscillator, the oscillator ceases to oscillate. When the blank is lined up with the foil, the oscillator continues oscillating. The oscillating/nonoscillating can be used to determine if the coded information is correct. Foley has a drawback in that it requires a decoder having complex circuitry.