GB678391A - Distribution of television signals or other carrier waves by wire line - Google Patents

Abstract

678,391. Preventing inductive disturbance; distributing music &c. COMMUNICATIONS PATENTS, Ltd., and KINROSS, R. I. March 20, 1951 [Jan. 9, 1950], No. 542/50. Class 40 (iv). Interference caused by the induction of longitudinal (push-push) currents in a two-wire line 11, 12 is reduced by the provision of series-connected inductors 15, 16 presenting high impedance to push-push current and low impedance to push-pull current and a shuntconnected centre-tapped inductor 21 presenting low impedance to earth to push-push current and high impedance to earth to push-pull current. The inductors 15, 16 are wound on a common core, are closely coupled, and are so connected that the magnetic flux resulting from a push-push current in the line is additive whereas that resulting from a push-pull current is subtractive. The inductor 21 has its two halves wound on a common core, closely coupled and so connected that the flux caused by a flow of push-push current to earth is subtractive whereas that caused by a push-pull current is additive. Additional inductors of either type may be employed if required. The invention is particularly applicable to distribution systems for television. Thus, television signals modulated on a 30 Mc/s. carrier are sent into the line by transmitter 13 and the inductors are connected between the line and the primary winding 17 of a balanced-tounbalanced transformer the secondary 18 of which feeds a co-axial cable 19 leading to a subscriber's receiver 14. The sheath of the cable and a screen 20 between the windings of the transformer are earthed.