| 摘要 |
<p>867,177. Supervising unattended repeaters. FELTEN & GUILLEAUME CARLSWERK A.G. Dec. 9, 1959 [April 10, 1959], No. 41842/59. Class 40 (4). [Also in Group XXXVI] In an arrangement for checking the ageing of unattended repeaters in a 2-wire carrier system in which two continuous alternating voltages of different frequencies lying in the Go or Return band are transmitted from one terminal station and intermodulation products are selectively returned from the repeaters, the two frequencies are so chosen as to form intermodulation products lying below the Go and Return bands, a band-pass filter BP is connected between the active part AV of each repeater and its lowfrequency shunt NFU, the band-pass filter BP of each repeater being tuned to a frequency below the Go and Return bands which frequency is characteristic of that repeater, and means is provided to prevent the frequency which is characteristic of any repeater from being produced by any other repeater. As described, the invention is applied to a system in which the Go band (A-B) is 24 to 224 kc/s. and the Return band is 312 to 552 kc/s., the directional filters TP1, TP2 and HP2, HP1 passing the respective bands in association with the common amplifier AV, feed current for which is transmitted via the low-pass filters of the power supply circuits S1 and S2 in the low-frequency shunt. These circuits also include high-pass filters which pass the frequencies below 24 kc/s., and the band-pass filter BP is connected between the output of the amplifier AV and the junction of these two high-pass filters. The two frequencies transmitted from A or B are so chosen that the intermodulation product of frequency less than 24 kc/s. falls within the pass-band of the filter BP of the repeater to be tested. The directional filter TP2 of each repeater is designed as a band-pass filter which rejects frequencies below 24 kc/s.</p> |
