GB785961A - Device for replacing a normally active apparatus in a transmission system or replacing a normally used route by a spare apparatus or a spare route in the event of a breakdown in the normally used apparatus or route - Google Patents

Abstract

785,961. Transmission systems. STANDARD TELEPHONES & CABLES, Ltd. Dec. 30, 1955 [Dec. 31, 1954], No. 37416/55. Class 40 (4). In a transmission system provided with standby equipment .8, 9, Fig. 2, or a spare route 2, the normal equipment 5, 6 is coupled to a consumer circuit 4 through a negative feed-back amplifier and a hybrid coil circuit, and fully operative spare equipment which is coupled to the amplifier output circuit, the feed-back path and a bias developing circuit feeds the load when the normal coupling conditions are changed by the blocking of the amplifier by the bias circuit upon failure of the normal equipment. Failure of the junction amplifier also results in the coupling of the spare equipment to the consumer circuit. In the junction arrangement, Fig. 4, the consumer circuit represented by R3 is fed normally by an input A to transformer T1, the input eb from the spare circuit B being suppressed by its manner of connection to the feed-back circuit. Circuit R1, C1 provides a standing bias for the valve V1 and a further circuit R6, C4 which is fed with the rectified output from transformer T takes down the working point of the valve when input A falls away. A transformer M which is saturated by the normal anode current is desaturated by the resulting fall of anode current and a large bias is provided by rectifier W1 from an auxiliary supply which may be the heater supply to ensure a definite cut-off. The circuit is prevented from operating when there is no input from the spare equipment by a rectifier W3 which is rendered conductive when the voltage across condenser C3 exceeds that across condenser C4. The Specification includes a mathematical analysis of the circuit.