Patent GB-386784-A (GB)
Title: Improvements relating to telegraph signalling apparatus
IPC: H04L25/42
Filed: 1931-12-24
Abstract: 386,784. Code telegraphy. IMPERIAL & INTERNATIONAL COMMUNICATIONS, Ltd. and HIGGITT, H. V., Electra House, Finsbury Pavement, London. Dec. 24, 1931, No. 35654. [Class 40 (iii).] In systems for receiving three types of signal elements, each made up of positive and negative half-elements, the circuits for registering dots and dashes are opened in alternate halves of the signal period. The output may be in ordinary cable code, or the output dots and dashes may be relatively displaced in phase. The Specification refers to a code of this type which enables the output of the receiver to be applied to a siphon recorder. The drawings show another system, in which for the received signals a space is (+ -), a dot (+ +), and a dash (- -), while for the sent-on signals separate dot and dash relays are left unexcited by spaces but are excited by dots and dashes respectively, for controlling a perforator for instance. Figs. 1 and 2 relate to a simplex system having a rotary distributer. The input relay has an armature RR which feeds the dot-storing condenser 21 through distributer segments 9, 11, 13, 15; and the dash-storing condenser 19 through distributer segments 8, 10, 12, 14. The dot distributer brush 16 picks up at the middle of the first half of the signal period while the dash brush 17 picks up at the middle of the second half. Hence the condensers are not charged by a space signal such as 2, 3, Fig. 1, their circuits being always broken either at the armature RR or at the brush ; but a charge is stored in the appropriate condenser when a dot 11 or dash 12 is received. The dot condenser 21 is discharged through brush 16, segments 22, 23, 24, and dot relay 30, while the dash condenser 19 is discharged through brush 17, segments 27, 28 or 29, and dash relay 32, the segments being so spaced that dashes are stored for a longer time' than dots, and hence dots and dashes are sent on in the right phase relation. The duration of the sent-on impulses is determined by hold-on segments 34, 35, 36, 38, 39, 60, which control locking windings 42, 44 ; it is 80 per cent of a signal period. ' Fig. 4 shows a two-channel multiplex system in which similar results are obtained by means of cam-operated contacts. The duration of contact in each case is shown by the thickened portions of the circles. The contacts 46; 47, for charging the dot condenser 21 are in series and their cams are separately variable for the purpose of adjusting the duration of the input impulse determined by their overlap. The dash contacts 48, 49 are similarly arranged, and these two pairs of contacts are so timed that the dot condenser- 21 is accessible for a brief interval at the middle of the. first half of the signal period, while the dash. condenser 19 is accessible at -the middle.of the second half. The dot sending- on relay 30A and dash sending-on relay 32A, with their locking relays 42A, 44A belong to one channel, and the corresponding relays 30B, 32B, 42B, 44B belong to the other, while the storing condensers 19, 21 serve both channels. The dot-discharging contacts 50A, 50B, and dash-discharging contacts 52A, 52B are so timed that dots and dashes are sent on. nearly in the normal phase relation. In a modification, Fig. 3 (not shown), dots and dashes are sent on out of phase with one another. In order that dots and dashes may occupy 80 per cent of the signal period, hold-on relays. 42A, 44A, 42B, 44B are provided, and are adapted to be cut off by contacts 54A, 56A, 54B, 56B. The hold-on relays 42, 44 may be dispensed with if the relays 30, 32 are neutral relays. Secret signalling may be effected by varying the -speed or by dividing the signals. amongst two or more channels in an arbitrarysequence. Specifications 238,622, 294,715, 328;945, [all in Class 40 (iii), Telegraphs,. Electric], and 384,691 are referred to.