| 摘要 |
PURPOSE:To simplify the device constitution, by detecting a digitized test signal tone with digital processing directly. CONSTITUTION:A signal tone transmitted from an analog exchange 2 generated at a test signal generating circuit 1 is converted into a digital signal at an analog-to-digital conversion circuit in a trunk 3. This signal is received at a digital signal reception circuit 51 in a signal tone detection circuit 5, and only the amplitude data is applied to an operation circuit 53. In the circuit 53, the amplitude data is compared or added with a preset comparison reference value or sum in a reference value designation circuit 52. The output pulse thus obtained is counted at a count circuit 54, the continuity of the output of a count circuit 54 at a prescribed time synchronized with a reset pulse 56 is discriminated at a continuity discrimination circuit 55, and the presence/absence of signal tone is discriminated. |
