SIGNAL RECEPTION CIRCUIT

PURPOSE:To decrease the code error rate, by measuring the level of a detection signal with two frequencies provided at the pre-stage of an FS data signal, selecting an inverting characteristic filter through the ratio, and compensating the unbalancing of the FS data signal. CONSTITUTION:Detection signal of two frequencies added prior to an FS data signal are inputted to an AC/DC conversion circuit 15 via a BPF 11, A signal detection circuit 16 produces an output when the converted DC signal is a prescribed value or over and gives a start signal to a microprocessor 18. The processor 18 stores the detection signal outputted from an A/D conversion circuit 17, operates the ratio of the amplitude of both the signal and gives a control output to an unbalance compensation circuit 14. The circuit 14 consists of a filter, the characteristic of which can be switched, so that both the detection signals are balanced with the output of the processor 18.