METHOD FOR CHECKING TONE FREQUENCY CHANNEL AND DEVICE WHICH IMPLEMENTS SAID METHOD Russian patent published in 2000 - IPC

FIELD: electric communication. SUBSTANCE: method involves temporal separation of transmission and reception of reference harmonic signal. When digital signal is transmitted to channel, method involves its filtration. Upon reception cycles, method involves integration of signal of transient process from input of tone frequency channel and its addition to part of reference harmonic signal in order to detect and differentiate basic harmonic frequency of summary signal. This results in production of test signal, which is equal to zero upon nominal resistance of tone frequency channel. Respective device has pulse generator 2, which opposite phase outputs are connected to control inputs of first and second gates 3, 4. output of reference frequency generator 1 is connected through attenuator 7 to adder 8 and through serial circuit of first resistor 6, first gate 3 and inductance coil 9 to capacitor 10, which is connected in parallel to tone frequency channel 11. Connection of first gate 3 and inductance coil 9 through serial circuit of second gate 4, integrator 13, which input is connected in parallel to second resistor 12, adder 8, low-pass filter 14 and differentiating circuit 5 is connected to amplitude detector 15. EFFECT: possibility to generate test signal, which amplitude describes deviation of tone frequency channel resistance from nominal value. 2 cl, 1 dwg