| 摘要 |
<p>1,154,668. Monitoring repeaters. C.T.I.- COMPAGNIE INDUSTRIELLE DES TELECOMMUNICATIONS. 29 Feb., 1968 [29 March, 1967], No. 9795/68. Heading H4R. In a device for the remote supervision of repeater amplifiers each repeater includes an oscillator, of frequency characteristic of that repeater, whose output is inhibited on detection at the repeater amplifier output of a signal whose level is within a predetermined small range. To monitor a repeater a frequency selective receiver at the monitoring station is tuned to the frequency characteristic of the repeater to be tested, and the output level of a variable frequency oscillator is adjusted until the selective receiver output disappears. By adjusting the frequency of the variable frequency oscillator the frequency response of the repeater amplifier may be tested. Fig. 2 shows a repeater using different frequency bands for the different directions of transmission and in which the test signal transmitted from one terminal station appearing at the output of the repeater amplifier 125, is amplified and applied to rectifier 127 to derive a D.C. control voltage proportional to the test signal level. The control voltage is applied to the bases of the opposite conductivity type transistors Q1 and Q2 which are so biased, from potentiometer 108, that one or the other conducts, to feed the output of oscillator 128 via transformer T4 to the input of the repeater amplifier, except when the control signal level is very nearly equal to the voltage from potentiometer 108. The frequency of oscillator 128 is arranged to be in the band to be returned to the monitoring station, or is transposed to that band after reception at the other terminal station. At the monitoring station the output of the variable frequency oscillator may be automatically adjusted to value which inhibits the production of the characteristic frequency at the repeater and a frequency response curve may be automatically plotted. The sensitivity of the oscillator inhibiting circuit may be increased by deriving the bias on the transistor Q1 and Q2 from different bias potentiometers. The oscillator may be inhibited by arranging the level sensitive circuit in the feedback path of the oscillator.</p> |
