Patent GB-436879-A (GB)
Title: Improvements in or relating to telegraph systems and apparatus
IPC: H04L1/08
Filed: 1934-04-20
Abstract: 436,879. Telegraphy. CREED & CO., Ltd., THOMPSON, A. E., and SALMON, R. D., Telegraph House, Croydon. April 20, 1934, No. 11945. [Class 40 (v)] In a printing telegraph system each code combination is transmitted a plurality of times and the corresponding character is recorded only if each received combination is identical or an error mark is made if the received combinations are not all identical. In the first embodiment the combination of impulses for each character of a five-unit code type. printing system are transmitted twice in succession together with starting and stopping signals and are received over line L, connected to a distributer arm 11 driven by a shaft 25. The arm 11 is at rest, between signals, on segment 1, being held by a latch 12 which releases when the start signal is fed through segment 1 to the magnet 13. The first five signal impulses are then distributed via segments 2 ...6 to polarized relays A ... E the earth return being completed through the upper contact associated with the switch arm 18. The relay armatures a ... e are thus set either on their left or right contacts for marking or spacing respectively. No circuit is completed on segment 7 and the arm 11 comes to rest on segment 1. The repetition of the same combination performs a similar cycle but during this second cycle the arm 18 is moved to its lower contact by a cam 16 on a cam-shaft 28 running at half the speed of the shaft 25. The impulses are thus fed to relays H ... N whose armatures h ... n are thereby set to marking or spacing. The marking contacts of the pairs of corresponding relays A, H, B, J, &c., are joined through printer magnets A1 ... E1 respectively and the spacing contacts through resistances r. When the arm 11 reaches the segment 7 at the end of the second rotation, the stop signal operates the relay ST if the two received combinations have been identical and also such of the magnets A1 .. E1 as are in circuit. The contacts st1 and st2 prevent the operation of the slow-acting error relay ER and operate the printing magnet F respectively. If the two received combinations are not identical the circuit of relay ST is not completed but that of relay ER becomes operative its contacts er1 and er2 energizing a magnet G to raise a mask into typing position and the printing magnet F respectively. The cam 17 on the shaft 28 ensures that the first code combination of each pair is always distributed to relays A ... E by operating the magnet 24 through delay mechanism 20, 21, 22, 27, 33 to release the latch 12 should the shaft 28 stop so that the arm 18 is in its lower position. This delay mechanism is described in Specification 339/35. In a second embodiment, Fig. 2 (not shown), the two successive received code combinations are fed to two printers of the type described in Specification 228,842, [Class 40 (iii)], the first of which has a distributer instead of a rotatable type wheel the other having a similar distributer in addition to the type wheel. If the two distributer arms are not set in identical positions an error magnet associated with the type wheel is energized instead of the printer magnet to print a special character.