| 摘要 |
<p>994,238. Line transmission systems; fault locating. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. May 6, 1963 [May 9, 1962], No. 17823/63. Heading H4R. In a transmission circuit including attended and unattended repeaters each unattended repeater includes a shunt impedance bridging the line and each attended repeater has an impedance measuring device in order that a break in the line may be located by a measurement of the impedance across the line. Fig. 1 shows a carrier telephone system comprising a source of carrier telephone signals 1 feeding a coaxial line 2, 3, 4, with intermediate unattended repeater amplifiers 5 and 6; power to the repeaters being fed over the line from a source 7, the carrier signals and the power supply being isolated at the repeaters by high and low pass filters 10, 11, 12, 13, 14, 15, 16, 17. The power flows through all the repeaters in series while Zener diodes 26 and 27 ensure continuity of the power supply circuit if one of the amplifiers is removed from circuit or develops a fault. Resistors 28 and 29 are in a eluded in the power circuit, the values being chosen to be less than the insulation resistance of the cable but higher than the series impedance of the conductors. In operation, should a break occur in any of the cable sections the impedance measuring device 30, measuring the impedance between the conductors of the cable, will indicate how many shunt impedances such as 28 or 29 remain in circuit and hence in which of the cable sections the break occurs. Subsequently the exact location of the fault may be determined by isolating the faulty section by means of switches 33, 34, and measuring either the capacity or the pulse echo time of the section of cable up to the break by means of a capacitance bridge or a pulse source and delay measuring apparatus 31, 32. In a modification, Fig. 2 (not shown) the shunt resistors 28, 29 have rectifier connected in series so that with normal power supply the diodes are back biased and the resistors absorb no current, for fault location the power supply is reversed so the rectifiers conduct and the fault is located as before.</p> |
