SURVEILLANCE SYSTEM, IN PARTICULAR FOR PERSONNEL REGISTRATION IN MINES

摘要

The system comprises a portable code-transmitter (transponder) (Fig. 1), a sensing unit (interrogator) Fig. 2 for receiving the signals of the code-transmitter, a signal processing unit 80 connected to the sensing unit, and a data-storing unit connected to the signal processing unit. The code-transmitter is a radio-transmitter (30) having a radio-frequency oscillator with inputs (31,32) connected respectively to a code-generator (10) and to a circuit (40) sensing a high-frequency magnetic field. The sensing unit has a coil L connected to an output of a unit 60 exciting the high-frequency magnetic field and having a control input 61. The sensing unit also has a code-receiver 50 with an input 51 for receiving coded signals from the transponder and outputs 52,53. The output 52 is applied to the control input 61 of the exciting unit 60 for interrupting the h.f. field, and the output 53 to the signal processing unit 80, preferably a microprocessor. IMAGE