There are a separate electronic chassis and two antenna panels, each containing both transmit and receive coils. Receive coils located in both panels detect the signal reradiated from a tag. Signal processing circuits trigger an alarm when appropriate. System E has an operating frequency greater than 500 Hz and less than 5 kHz. There are a separate electronic chassis and two antenna panels, each containing both transmit and receive coils.
Receive coils located in both panels detect the signal reradiated from a tag.
Signal processing circuits trigger an alarm when appropriate. System F consists of two panels, one a transmitter and one a receiver. The transmitted signal is a swept carrier operating above 1 MHz. Signal conditioning circuits perform alarm detection processing. System G has an operating frequency greater than 60 Hz and less than 5 kHz.