Improvements in or relating to three-wire systems for relaying two wireless programmes simultaneously

摘要

411,705. Distributing music &c. LEMON, E. N. KENT-, Newlaithes House, Horsforth, near Leeds. July 25, 1933, No. 20891. [Class 40 (iv).] In a two-programme distribution system comprising a two-wire circuit for one programme and a circuit over a third wire and a simplex on the two wires for a second programme, leakage unbalances between the two-wire circuit and the third wire are compensated by potentiometers across the two wires at spaced points throughout the system, the sliders being connected to corresponding points on the third wire at which switches are provided for opening the wire for testing purposes. One programme is transmitted from transformer 3 over the pair 1, 2 while the other is transmitted from transformer 6 over the third wire 5 and a simplex circuit over the pair 1, 2, loud-speakers for the second programme being connected between wire 5 and centre tapped chokes 9 across 1, 2. At various points along the system, the third wire is connected to the sliders of a potentiometer 10 across the pair 1, 2. The test man connects his set comprising head-phones 12 and centre tapped choke 13, in the manner shown, to the first point, opens line 5 beyond this point by the switch 11 and, when no programme is being transmitted over the simplex circuit, adjusts potentiometer 10 until a programme over 1, 2 is not heard. This adjustment is carried out at each point in succession.