GB351543A - Improvements in or relating to submarine signalling cables provided with repeaters - Google Patents

Abstract

351,543. Repeaters. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of Peterson, E.: 567, West 170th Street, New York, U.S.A.) March 27 1930, No. 9777. Convention date, March 30, 1929. [Class 40 (iv).] An amplifier in a submarine cable comprises a magnetic modulator serving to introduce a negative impedance to the frequencies to be amplified. The operation of the amplifier is dependent upon the fact that if two frequencies p, q are fed to a magnetic modulator a negative impedance to the lower of the two frequencies q is produced when the impedance of the system is low to the lower side band and high to the upper side band frequencies. In the system shown, Figs. 2 and 3, speech waves of frequencies 300-2000 and a continuous wave of frequency 250 from a generator 14 are fed over the cable L. At the repeating point R the low frequency 250 passes through a filter 19 to a harmonic generator HG designed to emphasize particularly the 10th harmonic, i.e. the frequency 2500, which lies above the speech band. This frequency (p), together with the speech frequency band (q) to be amplified, selected by a filter 17, are fed to the magnetic modulator MM, with which is associated a network 21 presenting a lowimpedance to the side-band 2p-q and a high impedance to all other frequencies. Amplification of the frequency band q, which may be the whole speech band or only the higher frequencies according to the width of the filter 17, is thus produced. By suitably designing the network 21, the amount of amplification may be made dependent on the frequency thereby compensating for unequal attenuation in the cable. The degree of amplification is dependent upon the amplitude of the wave supplied by generator 14 and may thus be varied at will from the terminal station by means of the potentiometer 15. The cores of the harmonic generator HG, the magnetic modulator MM and other inductances are preferably of nickel-iron alloy to economize space in the cable. The whole apparatus at a repeater point may be accommodated within the cable sheath. Specification 142,115, [Class 40 (iv), Telephones &c.], is referred to.