Patent GB-285955-A (GB)
Title: Improvements in apparatus for transmitting and receiving telegraphic messages in code
IPC: H04L9/38
Filed: 1926-11-19
Abstract: 285,955. Damm, A. G. Nov. 19, 1926. Secret signalling; systems using code elements distinguished by duration of current; electric synchronous movements and synchronism indicators. -In a wireless or other system for automatically enciphering, transmitting, and deciphering Morse messages the original message is divided into sections the first of which is mutilated in transmission by combination with a key section, while each subsequent section is mutilated in transmission by combination with a slightly modified form of the preceding section. The, cipher code consumes less current than the Morse code. Synchronism is maintained by the signals themselves. Cipher. The line X, Fig. 3, shows the word PARIS in Morse, the line Z shows the cipher message actually transmitted, and the line Y shows the series of confusing impulses with which X is combined to produce Z. The process of combination consists in including in Z all marks peculiar to either X or Y while omitting from Z all marks which are common to X and Y. To reproduce X, Y and Z must be combined according to a similar rule, since X will contain only those marks which are peculiar to either Y or Z. To obtain the line Y, the message is divided into equal sections each of which comprises an even number (taken as 10 in Fig. 3) of time units each equal to the duration of a dot. The first section Y, of Y comprises an arbitrary key consisting of a number of dots falling in odd-numbered time elements (the 1st, 5th, 7th and 9th in Fig. 3). The second and nth sections of Y are respectively identical with the first and (n-1)th sections of X, modified in that all even-numbered time intervals are rendered empty : thus the marks in the fourth and eighth time-intervals cf the first section of X, Fig. 3, are omitted in the corresponding (second) section of Y. Enciphering and deciphering device : principle of action. At the sending station (right of Fig. 4) the original message X, consisting of positive impulses, is delivered to the terminal 202 and lamp L2 while the positive impulses constituting the confusing signals Y are delivered to the terminal 201 and lamp L1. The relay R is energized' and a. signal is consequently emitted if an impulse arrives on either side alone, but if X and Y signals reach the two sides of the relay coincidently the relay is unaffected. The signals emitted therefore conform to the cipher Z. At the receiving station the cipher signals Z are applied to lamp L<1>2 and the confusing signals Y, produced locally by apparatus similar to that at the sending station, are applied to the lamp L\. The recorder relay R<1> therefore records the message X in clear. Sending station (right of Fig. 4). When the switch k at the sending station is set to the right, as shown in full lines, all circuits passing through it are broken except that of the commutator ring A, which emits synchronizing signals. When the switch k is set to the left the ring A is cut off at 3 and the relay Rt is energized by the first impulse from the tape T over contacts 7, 6, 13, 12, 9, 8, and this relay holds on over contacts 12, 14, 4, 5. The original or X message from the tape T then reaches the lamp L2 through contacts 7, 6, 16, 15; it also reaches the brush bC, and the signals are consequently stored in the magnets 154, as described below, for subsequent emission as Y signals through the ring D. While one section of the message is delivered to the lamp L2 in clear, the preceding section, having been stored in the magnets 154 (of which only one is shown in Fig. 4), is delivered to the lamp L1 through the contacts 18, 17, 1, 2, after passing through the ring D which modifies it into a Y section owing to the fact that the ring segments, each of which corresponds to one time unit, are alternately insulating and conducting. The relay R therefore emits a Z or cipher message. The first section of the confusing series Y is stored in a combination of pins 183 connecting segments of the rings B, C, as described below. This is delivered to the storing magnets 154, for transmission through the brush bD, until the relay Rt is energized by the starting of the message. Thereafter the ring B is cut off at the armature 11<b> and the ring C takes its place, so as to effect the storing of each section of the X message for combination as a Y section with the next X section. Receiving station (left of Fig. 4). On the cessation of synchronizing impulses in the line the relay R<1> is operated by the now unbalanced impulses from the ring A<1> and (the switch SW being closed) the relay Rr is consequently energized through the armature 203, cutting out the brush bA<1> at 21, cutting in the brush bC<1> at 137, and closing a hold-on circuit at 24. The next line impulse, by energizing the hold-on relay Rr, cuts out the brush bB<1> at 27 and cuts in the brush bD<1> at 33. Thereafter while the cipher message Z is delivered as received to the lamp L<1>2 the message Y is delivered to the lamp L<1>1 through the brush bD, and the message X in clear is consequently recorded by the recorder R', so that positive impulses in Morse pass from the armature 203 through the contact 137 to the brush bC<1> and so are stored in the group magnets 154<1> for delivery through brush bD<1> to the lamp L<1>1. Device for storing signals. The storing devices at the transmitting and receiving stations are both constructed as shown in Figs. 5, 5a. The successive sections of the message X are modified and stored by delivering the elements to the brush bC and so through successive segments 139 of the ring C and corresponding magnet coils 154 to negative via the ring 142, brushes 148 and 124, and ring 117. Any magnet 154 which is thus energized raises its core 155 and so permits a lever 156, Figs. 5, 5<a>, to make contact with a stop 158, and to connect the corresponding segment 141 of ring D (this segment being electrically continuous with the pin) to positive through the lever 158, discs 132, 134, brushes 147, 129, and ring 122. Those segments 141 which have thus been connected to positive subsequently reach the brush bD (not shown in Figs. 5, 5<a>) and deliver the signals thus stored in them, as described above; they are then reset by the hook 164, and are retained set by the cores 155, which drop into place. The brush bD is carried bv an arm 114 which can be moved about the shaft 102 so as to vary its angular distance from the brush bC, in accordance with the number of time-units in each section into which the message is divided. The initial arbitrary section Y1, Fig. 3, is set up at each station by screwing down selected pins 163 so as to connect together corresponding segments 139, 140 of the rings C, B. Thus the initial section Y1 is stored in the magnets 154 by impulses passing from positive through the ring 120, brush 127, brush bB, segments 140, selected pins 163, corresponding segments 139, and corresponding magnets 154 to negative. As soon as the message begins, the ring 120 is cut off from positive at 11<b> or 27, Fig. 4. Synchronization. Before the message begins synchronization is established by hand, after which it is maintained by the signals. Half of the ring A, Fig. 4, comprises a conducting segment 142, Fig. 5, which is connected through 134, 147, 129 and 122 to positive. When the switch k, Fig. 4, is to the right, long dashes are sent to line owing to contact of the brush bA with the ring A; long dashes are thus delivered to the lamp L<1>2 at the receiving station. Further, while the switch SW is open, long dashes are delivered to the lamp L<1>1 from the brush bA<1> and ring A<1> at the receiving station, and the behaviour of the lamps L<1>1, L<1>2, and recorder R<1> guide the operator in securing synchronism by manual adjustment of a friction gear which drives the table 104, carrying the commutator brushes, through the shaft 107. On the other hand, when the switch k is to the left and the switch SW closed, synchronism is maintained by the signals, a slight phase-difference between the receiver-commutator and the signals causing the energization either of the magnet Ma, Fig. 4, which relieves the pressure of a brake pad normally applied to a disc on the shaft 107, or of the magnet Mr, which applies an additional brake pad to the disc. The signal impulses energize the relay Rs, and consequently the relays S1, S5, while the combination impulses from the brush bD<1> energize the relay RS1 and consequently the relays S1, S4. The relays Ma, Mr are unaffected if a local impulse begins simultaneously with a line impulse, for their circuits are then broken at 40, 47; or if S1, S3, become energized at the instant when S2' S5 become de-energized, or vice versa. In the former case, for instance, the circuit of the relay S3, controlling Ma, is broken at 38, and that of the magnet Mr is broken at 47. If, however, the local impulses through Rs should lag slightly behind the line impulses through Rs1, then on receipt of a line. impulse the relay S2 gives negative to S3 at 38, and shortly afterwards S1 gives positive to S3 at 37, and consequently S3 gives positive to the accelerating magnet Ma at 42. When the positive at 61 is cut off, S3 and Ma still find negative through the hold-on contact 45, while Ma attains positive through the armature 40 owing to the de-energization of relay S2. Energization of Ma and S3 continues until the cessation of the local impulse cuts off positive at 59. Meanwhile the retarding magnet Mr is cut off from positive at 55 until the local impulse begins, and at 47 thereafter; and before contact is restored at 47, positive is cut off at 61 owing to cessation of the line impulse. Similarly, if the local impulses lead the line impulses, the retarding magnet Mr comes into operation.