Patent GB-625250-A (GB)
Title: Improvements in signalling systems
IPC: G01S1/02
Filed: 1945-03-13
Abstract: 625,250. Electric selective signalling. MARCONI'S WIRELESS TELEGRAPH CO.. Ltd., CLOUGH, N. H., and OLIVER, E. C. March 13, 1945, No. 6299. [Class 40 (i)] An electro - mechanical signalling system for controlling the transmission of a sequence of signal elements, which may be either of two kinds, e.g. dots or dashes, comprises a plurality of sets of switch contacts each including at least two contacts respectively appropriate to the two kinds of signal elements and each available for determining the kind of signal element to be transmitted for one element of the sequence, and a signal transmitter controlled by each set of switch contacts in turn, in accordance with the setting thereof, by means of a sequencestepping device adapted to explore the switch-contact-sets in turn to derive the sequence of signal elements. As shown, for automatically controlling the transmission of the interlocked A/N or E/T morse signals of a radiorange, and the interposed call sign of the station, the circuit elements comprise (1) a pulse generator supplying at contacts pl, Fig. 1, pulses of equal duration and spacing equal to one baud, to (ii) a discriminator circuit DC which distinguishes between dots and dashes, (iii) an interval timing unit int, Fig. 2, which measures the interval between the course signal and call sign transmissions, (iv) an interval selecting switch IS, Fig. 5, which determines certain interval durations, (v) an interval counting circuit ICC, Fig. 2, which measures the interval durations determined by the switch IS and also the duration of transmission of the course signal as determined by the setting of (vi) a switch 2S, Fig. 5, (vii) a sequence switching circuit SSC, Fig. 3b, (viii) character selecting keys CSK, Figs. 4a, 4b, for selecting the letters of the call sign, each key row being appropriate to a letter and each key in a row selecting an element of that letter, dot or dash, in the upper and lower positions, respectively. The two - letter call sign is transmitted twice, once into the A lobe of the course signal and after a five-baud interval, into the N lobe, the respective lobes being identifiable by a pilot by characters such as E, W transmitted respectively into the A and N lobes after the call sign. These characters are provided for by the lower row of keys CSK. Discriminator circuit. Assuming that an interval precedes transmission of the A/N signals and that all relays are restored, the first pulse over contacts pl, Fig. 1, operates a relay TA which locks in series with the upper winding of a relay TB as the pulse ends. The second pulse energizes a relay TC in series with the lower winding of TB. Relay TA releases immediately and TB, TC release as the pulse ends. Relay A is energized by the third pulse to start the next cycle which is thus of 4 bauds duration and is repeated until the circuit is modified at contacts dt<SP>1</SP> or sc2. Initial blank interval measuring. Assuming the interval is to be a minimum switch IS, Fig. 5, is set, as shown, to position 1. When relay TA first energizes, a relay IM, Fig. 2, energizes over contacts ta6, and locks in series with a relay IB as TA releases. When TA is next energized, the positive at contacts ta6 energizes a relay 2M over operated contacts 1b3, relay 2M locking in series with relay 2B as TA restores. When relay 2B operates, a relay SP, Fig. 4b, operates over contacts 2m4, cs1, 2b1, switch IS, Fig. 5, and contacts ba1, ch3. Should the interval selecting switch IS be otherwise set, further operational cycles of relay TA would energize successively the relay pairs 3M, 3B, 4M, 4B, &c. in the ICC until the circuit of relay SP is completed over the switch IS and the appropriate contact 2b1, 3b1, 4b1 ... , Figs. 4a, 4b. Relay SP at contacts sp4, Fig. 2, restores all the operated relays IM, IB, &c. in the ICC. In the sequence switching circuit SSC, Fig. 3b, a relay MA is operated over contacts Ib1, ba3 when relay IB operates, and when IB releases on operation of SP, as above described, MA locks in series with a relay BA, whereupon SP is restored by opening of contacts ba1, Fig. 5. Transmission of course signal. Over operated contacts ba1 a relay CS is operated and the ICC circuit, Fig. 2, is removed from control by the discriminator circuit DC at operated contacts ba5, Fig. 2. When relay TA again operates the fifth pulse, a relay DT, Fig. 3a, operates over operated contacts ta2 and cs4, Fig. 3b, in series with a relay MD in the SSC. Contacts dt1 cut relay TB out of the discriminator circuit, Fig. 1. A relay OM, Fig. 6, now operates over contacts cs3, md4 and locks over om2. A relay CR operates over contacts om3, md3, cs2 and over contacts om4 a relay CM is operated. Contacts cr3, Fig. 6, operates highfrequency switching means in the transmitter and contacts cm3 connect up the tone-modulating means therein to transmit into the A lobe of the course signal field pattern. As relay TB is now cut out of the D.C. relay, TA restores at the end of the fifth pulse (i.e. the ninth baud), whereupon relay DT restores and a relay BD, Fig. 3b, operates in series with MD. Operated contacts bd4 restore relay CR which at contacts cr3 restore the H.F. switching means in the transmitter. These conditions persist during the tenth baud. The energization of relay CR corresponds to the transmission during the ninth baud of a dot, the first element of Morse totter A radiated by the A lobe followed, during the tenth baud, by a space. When relay TA operates at the eleventh baud +ve over contacts ta3, Fig. 3a, energizes a relay ME in the SSC, Fig. 3b. Relay CR,Fig. 6, operates over contacts me3 and contacts cr3 effect transmission into the A lobe for three bauds (the second element of the A) when TA, TB, in the D.C. release and allow BE to operate in series with ME, whereupon CR is released at be4. For the 14th and two succeeding bauds CR is kept restored to give an interval of three bauds before the next transmission of letter A. During the 15th baud, a pulse period, relays SC, Fig. 3a, and MF, Fig. 3b, are operated in series over contact ta4. Contacts sc2 modify the D.C. so that TA releases as the 15th baud ends to restore SC and allow relay BF to operate in series with MF, whereupon the relay pairs MD, BD, ME, BE, MF, BF are successively restored. The cycle of operations performed during the 9th to 16th bauds (i.e. initiated by the fifth pulse) is now repeated during the 17th to 24th bauds and so on to radiate the Morse signal A continuously into the A lobe. Radiation of the N into the N lobe is complementary to radiation of A into the A lobe and is offected by the continuous energization of relay CM for this duration of course signal transmission. Initiation of call sign. The interval timing unit int, Fig. 2, delivers short pulses at intervals of e.g. 30 secs. Assuming the course signal is to be transmitted for 2 minutes, switch 2S, Fig. 5, is set to position 4 to multiply the 30 sec. interval by 4. As above described, the ICC circuit is removed from control by the D.C. at contacts ba5 at the commencement of course signal transmission, whereupon the first int pulse operates relay IM over bb4, ba5 and at the cessation of the pulse relay IB operates in series with IM. The second int pulse similarly operates the relay pair 2M, 2B and so on for the subsequent pulses until relay 5B operates. When now the relay BF operates as above described, at the end of an A/N transmitting cycle, relay SP, Fig. 4b, is operated over contacts 5b1 and the contact 4 of switch 2S, Fig. 5, whereupon contacts sp4 cause as before release of all ICC relays 1M, 1B .... A relay MB in the SSC, Fig. 3b, energized over contacts 1b1 when relay 1B operated, now remains held in series with a relay BB. Relays SP, Fig. 4b, CS, Fig. 5, are restored at contacts bf1, bb1 and relays CR, CM, OM, Fig. 6, are restored at cs2, cs3 to stop the course signal transmission at cr3, cm3. An interval is now interposed by operations similar to those during the initial blank interval, the only difference being that as MA, BA, MB, BB are now energized the relay pair MC, BC function in lieu of MA, BA. Call sign transmission. Assuming X to be the first letter of the call sign, the Morse elements thereof are composed by setting the keys in the top row of CSK; K1, K4 being down (dash) and K2, K3 up (dot position), K5 being unoperated. When relay BC operates in series with MC, as indicated above, a relay CP, Fig. 7, operates over contacts me3, bc5 and locks over cp6, whereupon relays MA, BA restore at contacts cp5 causing catenary restoration of MB, BB, MC, BC. As BC restores, a relay CH, Fig. 7, operates over bc5, cp4, relay CR, Fig. 6, operates over contacts oh3, Fig. 5, and line d to switch at contacts cr3 the H.F. transmission into the A lobe. Relays A, AX, Fig. 5, are also energized over contacts ch3 and lock over ax3. Contacts ch5, Fig. 2, connect the ICC to the CSK. When relay TA, Fig. 1, is next energized, +ve over contacts ta2, Fig. 3a, energizes relay DT over line C, Figs. 4b, 4a, in series with OM, Fig. 6, and as the pulse ends, relay OM locks in series with OB as DT restores. As the next four baud cycle of the D.C. is initiated by energization of relay TA, a relay CD, Fig. 4a, operates over a circuit including operated contacts of key k1 and a1. Relay IM in the ICC also operates for the first three bauds of the D.C. cycle over other operated contacts of key k1 and contacts a5. At operated contacts cd1, Fig. 6, modulation. tone is connected to the A lobe transmission for the three bauds, i.e. to transmit the first dash of letter X. At the end of the three bauds, relay CD restores and relay 1B operates in series with 1M as before and at contacts 1b2, 1b3 associates key k2 with relay 2M in the ICC. At the next operation of relay TA, Fig. 1, i.e. after an interval of one baud, relay DT, Fig. 3a, operates in series with 2M, Fig. 2, over a circuit including operated contacts of key k2 and a6, and