| 摘要 |
PURPOSE:To measure the level of call signals and pilot signals, and specific channel of a lot of telephone sets easily and accurately, by changing over the signal level of each channel the pilot signal level and the entire level of carrier lines transmitted multiplexly by means of a switch. CONSTITUTION:An input signal undergoes impedance matching and level adjustment, and detected heterodyningly at a heterodyne detection circuit consisting of a modulation circuit 2 and an oscillator 9, and the detection output is supplied to band pass filters 3, 4 and 5. In a figure, TONE is a sound frequency band signal and RNG shows a calling signal. The selected channel signal is amplified at an amplifier 6 via a selection switch S3 and indicated on a meter 7. Further, the amplified signal is extracted from an output terminal 8. The selection of the channel and pilot signal is performed by changing over the frequency of a local oscillator 9 by a switch (not shown). The switches S1, S2 are interlocked, and in selecting the switches to the opposite position from the position shown in the figure, the device is a conventional level meter, allowing to measure the overall level of all the channels. |
