Patent GB-643322-A (GB)
Title: Improvements in correcting arrangements for telegraphic systems utilizing a start-stop equal length code
IPC: H04L25/24
Filed: 1946-09-26
Abstract: 643,322. Code telegraphy. COMPAGNIE GENERALE D'ELECTRICITE. Sept. 26, 1946, No. 28820. Convention date, Dec. 20, 1945. [Class 40 (iii)] In a signal correcting device for a start-stop telegraph system in which a relaxation oscillator produces short pulses spaced by an interval of time equal to the duration of an undistorted signal element and applied, in dependence on the operative position of a relay responsive to the incoming signals, to one or the other winding of a relay transmitting positive or negative signal impulses to an outgoing line, the oscillator is operated to provide a first pulse at the mid-point of the theoretical duration of the start element by connecting the cathode circuit of the valve of the oscillator to the armature of a starting relay having a winding connected to the input terminals of the device through a rectifier allowing the passage only of currents whose polarity corresponds to the start signal element and the operation of the relay is retarded by an interval equal to half the theoretical duration of a signal element. The start relay REL1 which receives the line signals is witheld from operation by the stop current-normally positive-on the line by means of the rectifier RED. A short interval, e.g. 10 milliseconds, determined by the condenser C1 and resistance R1, after the current changes to negative at the beginning of the start impulse, the relay REL 1 operates and at contact T connects earth to the cathodes of the valves L1, L2 of two relaxation oscillators, the former being tuned by R2, C2 to produce the impulses at signal element intervals, e.g. 20 milliseconds, and the valve L2 being associated with condenser C3 and resistance R3 to provide short pulses, spaced apart by a time corresponding to the transmission of a complete signal, e.g. 120 milliseconds, and applied to a winding (3) of a reset relay REL2 having a winding (1) biassing the relay to the unoperated position. The first impulse produced by the valve L2 is without effect since at this time a current corresponding to the sense of the start signal element is passing through the winding (2) of the relay REL2 and this relay is arranged to be operated by an impulse from the valve L2 only when the current through the winding 2 corresponds to the stop element. Also the relay REL1 is not affected since the current through winding (1) is of greater effect than that through winding (2). The signals received at E operate a relay REL4 and according to the position of its armature when the impulses are generated by the valve L1 either the winding (1) or the winding (2) of the,relay REL3 is energized so that a positive or negative impulse of the correct duration is applied to the output terminals S. The circuit of the valve L2 is triggered by the seventh impulse generated by the valve L1 and applied over a transformer T4 and resistance R5 in its input circuit. The impulse produced by the valve L2 is aided by the current through the winding (2) of the relay REL2 so that the opposing action of the winding (1) is overcome. Relay REL2 operates and at its contacts T restores condensers C1, C2, C3 to their original voltage conditions. Current is also passed through the winding (2) of the relay REL1 which moves its armature to the rest position R in which earth is disconnected from the valves L1, L2. A number of correcting devices may be employed and can be synchronized by an impulse applied over a transformer T3 and resistance R4 in the input circuit of the valve L1. Specification 634,292 is referred to.