| 摘要 |
<p>1,145,038. Unattended repeaters. FELTON & GUILLEAUME CARLSWERKE A.G. 24 Nov., 1967 [9 March, 1967], No. 53509/67. Heading H4R. In an arrangement for monitoring unattended repeaters in which a test signal of a frequency allotted to each repeater is extracted and fed back to the line changed in frequency, as in Specification 828,061, the test signal is selected by a filter formed by a crystal Q and the high impedance winding W of a transformer of which the low impedance winding is part of the highpass T-network 6 of the current supply circuit. The crystal filter thus has a low input impedance in relation to the characteristic impedance of the line. A resistance R, and if desired, an LC filter may be provided in the input to the frequency-converter U, which may double the frequency. The transmission characteristics of the repeater may be observed at the end from which the test signals are sent, and the noise may be measured at the other end.</p> |
