TONE SIGNAL DETECTOR CIRCUIT

摘要

PURPOSE:To secure an assured detection of the tone signal by giving the negative feedback to the band-pass filter input of one side from the back of the band-pass filter and offsetting the frequency component of one side before the band-pass filter of the desired frequency to each other. CONSTITUTION:The signals transmitted in double frequency parallel of i1 and i2 and piled on the aural signal are transmitted to low pass filter 2 from detector output terminal 1 of the reception part, thus amplifying (3) the double frequency parallel tone frequency of the micro-level. The signals which received limiation through amplitude limit circuit 6 and 11 pass through band-pass filter 7 and 12. Here output i1 of filter 7 is negatively fed back to the intermediate point between resistance 9 and 10 through resistor 16 and 17, and at the same time output i2 of filter 12 is negatively fed back to the intermidiate point between resistance 4 and 5 through resistor 14 and 15 respectively. As a result, only i1 is transmitted as for detector 8 with an ample level margin secured, thus ensuring the stable detection. The same procedure is applied also to the detection of i2.