Block diagram of a district (rural) wired broadcasting subsystem: (ASD) amplifier station for the district subsystem, (DF) distribution feeder line, (FT) step-down feeder transformer, (ST) step-down subscriber transformer, (SS) subscriber loudspeakerĭuring the 1930’s, a number of countries, including Germany, Austria, Italy, and Switzerland, developed systems for multiple-program wired broadcasting over the telephone networks. In rural areas, networks use both overhead lines and underground cables, chiefly with aluminum current-conducting cores.įigure 2. In cities, the distribution networks for wired broadcasting usually use overhead lines of steel or bimetallic (steel-copper or steel-aluminum) wires. The stations of such subsystems receive broadcast programs from the nearest radio transmitting station, and the subsystem is switched on and off automatically by a coded command transmitted from this same radio station. Consequently, in those locations where radio reception is reliable at ultrashort waves, automated rural wired broadcasting subsystems are often installed. The reliability of these lines and the quality of the sound in the programs being transmitted is somewhat lower. In addition to a distribution network of feeder lines for the district center, the station is connected to long (up to 40 km) feeder lines leading to neighboring populated areas. The broadcast program is fed to an amplifier station in a district center via a long-distance broadcast channel, or it is picked up by a radio receiver at the station. Block diagram of a district wired broadcasting subsystem in a major city: (CAS) central amplifier station, (SAS) support amplifier station (these are situated in various districts In the city and are equipped with powerful audio-frequency amplifiers for supplying the distribution network), (TS) step-down transformer substation, (ST) step-down subscriber transformer, (SS) subscriber loudspeaker, (CL) connecting line, (MF) main feeder line, (DF) distribution feeder line, (SL) subscriber lineįigure 2 shows a diagram of a rural wired broadcasting subsystem. High operating reliability in the subsystem is ensured by having backup amplifiers, by supplying transformer substations over two feeders from different support amplifier stations, and by providing a system for detection of failures in the network.įigure 1. In smaller cities and urban areas, a wired broadcasting subsystem may consist of only three, two, or even one section (see Figure 1). All amplifier stations and transformer substations of the major wired broadcasting subsystems are automatic and are remotely controlled from the central amplifier station.
It is usually 960 volts in the main feeder lines, 240 volts in the distribution feeder lines, and 30 volts in the subscribers’ lines. The operating voltage varies in the various portions of the distribution network. The program for the broadcast is fed to a central amplifier station from a local radio studio or through a station of the longdistance telephone communications service from a radio studio of the oblast or republic or from a studio in Moscow. Figure 1 depicts a block diagram for a single-program wired broadcasting subsystem that covers a major city. Single-program wired broadcasting is conducted at audio frequencies. 1, 1974, there were more than 20,000 subsystems and approximately 55 million subscriber loudspeakers. By the beginning of the Great Patriotic War (1941–45), there were more than 11,000 subsystems in the independent broadcasting network, serving approximately 6 million subscriber loudspeakers on Jan. The initial system, with a power of 40 watts, was set up in Moscow in 1925 it accommodated 50 loudspeakers located along the streets. Single-program wired broadcasting was first developed in the USSR. There are both single-program and multiple-program types of wired broadcasting. A system of sound broadcasting in which, unlike radio broadcasting, the sound (speech and music) is transmitted to a large number of listeners (subscribers) by means of electrical oscillations over a wired network-either an independent broadcasting network or a telephone network.
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