Patent GB-267180-A (GB)
Title: Improvements in and relating to electric telegraphic systems
IPC: H04L25/20
Filed: 1925-10-14
Abstract: 267,180. Higgitt, H. V., and Eastern Telegragh Co., Ltd. Oct. 14, 1925. Transmitting and receiving systems for code telegraphy.-In a system employing the Morse code a dot is represented by a marking signal for substantially half a time element followed by a spacing signal for the remainder of the time element, a dash by a marking signal for substantially a full time element, and a space by a spacing signal for substantially a full time element. The invention is applicable to single current or double current working or to any system in which marks and spaces are distinguished by currents of different polarity or strength. Perforated-strip transmitters.-The signals may ba transmitted from a tape perforated according to the cable code by the use of the automatic transmitter described in Specification 5017/15 with slightly modified cam and detent arrangements, or by the use of a modification, Fig. 7. ot the automatic transmitter described in Specification 19099/05. Either pecker 13 or 14 on entering a hole in the tape closes a corresponding contact 15 or 16, and cams 18, 19, 20 controlling contacts 21, 22, 23 respectively are mounted on a shaft geared to the tape feed wheel to make one revolution per centre hole. The gearing is arranged to allow the cam 18 to close the contact 21 when the peckers are opposite to a centre hole. The cams 19, 20 open their contacts 22. 23, 180‹ and 360‹ respectively after the closure at 21. Closure of the contact 15 or 16 simultaneously with the closure at 21 operates the sending relav 27 and operates also the corresponding dot flick relay 24 or dash flick relay 25. The tongues of the relays 24, 25 thus close hold-on circuits for the relay 27 which are opened at the contacts 22, 23 after a half and a full time element respectively. Restoring or modifying imperfect signals; repeating systems using contact-making relays; receivers with mechanical source of power; perforated-strip recorders.-The signals ma be received by a modification, Fig. 6, of the apparatus described in Specification 234,179. The synchronized shaft 1<a>, making one revolution per signal element, carries a cam 1 designed to move forward the hammer 2 in two steps, and a signal selector 6 controlled by a magnet 6<1> is arranged between the hammer 2 and the dot and dash selectors 4, 5 controlled by magnets 4<1>, 5<1> respectively. According as the line relay 3 is on its marking or its spacing contact the energizing of the magnets 6<1> and 5<1> or of the magnet 4<1> is effected. Thus, on receipt of a marking current, the selector 6 is moved forwards by the first step of the hammer 2 and the selector 4 or the selector 5 is moved forwards by the second step, according as the signal is a dot or a dash, to actuate the levers 7, 8 respectively of the receiving, retransmitting, or strip-perforating device. In a modified arrangement, Fig. 8, two relays 81, 82 are operated similarly by the line currents, and the marking and spacing contacts of the relay 81 are connected as shown through the magnets controlling the dash and dot selectors 84, 83 respectively to the marking contact of a relay 92 ccntrolled by the relay 82. The synchronized shaft 1<a> carries cams 85, 86 actuating the hammers 88, 89 associated with the selectors 83. 84 respectively and a cam 87 actuating a lever 91 between contacts 91<a> and 91<b>, this lever moving to the right half a revolution before the movement of the hammers to the left. The contact 91b is connected to the tongue of the relay 82, the contact 91<a> is connected to - battery, and the lever 91 is connected through a condenser 90 to + battery. The condenser 90 is thus, during the first half of each signal time element discharged through one or other coil of the relay 92 according as a marking or a spacing current is being received, and during the second half of a time element following a marking current in the first half the dot selector 83 or the dash selector 84 is actuated according as a spacing or marking current is then being received. Received cable code signals may be converted for retransmission according to the invention by the use of apparatus as described in Specification 234,179 to control the contacts 15, 16, Fig. 7. Distributor systems.-As the times required for signalling a dot, a dash, and a space are equal, multiplex operation may be effected by applying a single dot, dash, or space to each channel in turn.