| 摘要 |
1495519 Wired distribution systems SIEMENS AG 19 Dec 1974 [21 Dec 1973] 54842/74 Heading H4R In a signal distribution system, e.g. for distributing television signals, in which signals are distributed from a central station over a network having a number of levels, a distributer network level includes a number of remote powered line amplifiers and the feed in of power to, and the fault monitoring of, the line amplifiers are carried out commonly at a number of signal transfer points from the distributer level to a lower level, the remote feed direction in the distributer level being opposite to the signal transmission direction. As described Fig. 1 shows the distributer level from a central station A to local networks connected at points D, E, F, G, H, J, K, L and M, which are preferably arranged at telephone exchanges. D.C. isolation is provided at the break points in the network, indicated by capacitor symbols, and power for the line repeater amplifiers is fed in at the points D, E, F, H, J, L and M. Each amplifier can be of the type shown in Fig. 2 which includes an oscillation OG providing a controlled characteristic frequency which is fed to the inputs of the amplifiers of the repeater and can be received and monitored at the transfer points, D to M, to the local networks. In addition a circuit SZ is provided at each repeater to detect a break in the D.C. loop on the signal input side of the amplifiers, and to bridge the D.C. supply loop, from a to b, to maintain power supply to all the amplifiers on the side of a fault remote from the central station, to allow identification of the fault location by the presence of the characteristic oscilllations at the transfer points. With the transfer points located at local telephone exchanges the power may be derived from the exchange supply, via a converter if necessary. Other intermediate amplifiers and transfer points are described with reference to figs. 3 to 5. |
