GB1109566A - Improvements relating to a transmission line section - Google Patents

Abstract

1,109,566. Repeater systems. CIT-COMPAGNIE INDUSTRIELLE DES TELECOMMUNICATIONS. 25 Nov., 1965 [26 Nov., 1964], No. 50230/65. Heading H4R. Pilot-operated automatic volume control and faulty repeater locating system utilizes, for regulation of each section between adjacent repeaters a different pilot frequency, the frequencies of adjacent sections differing by the same value so that the pilot frequency varies in arithmetical progression along the line. All the pilot frequencies are received at the terminal station to be detected and used to locate a faulty repeater. Fig. 2 shows a typical repeater amplifier A<SP>1</SP>m of a system, the output of the amplifier being mixed in T<SP>1</SP>m with the pilot frequency F m for the succeeding repeater section. In addition the locally generated pilot frequency F m is used to modulate the repeater amplifier output which includes the pilot frequency F m -f, of the preceding section. The difference frequency f, e.g. 1000 c/s., which will be the same in all repeaters of the system, is extracted by filter 2, rectified, compared with a reference V o and the difference used to control the gain of the amplifier A<SP>1</SP> m . In a two-way system, Fig. 1 (not shown), the pilot frequencies along the direction of transmission in one channel are arranged to increase, while in the direction of transmission in the other channel they decrease and the same pilot frequency generator is used at each repeater station for both directions of transmission. At the terminal station a main pilot may be extracted to provide overall compensation of the line, while all the individual repeater section pilots are monitored to provide fault location. The repeaters may include transistor amplifiers.