Patent GB-328945-A (GB)
Title: Improvements relating to telegraph transmitting and retransmitting apparatus
IPC: H04L15/18
Filed: 1929-02-05
Abstract: 328,945. Wood, K. L., Hubble, W. C., Higgitt, H. V., and Eastern Telegraph Co., Ltd. Feb. 6, 1929., Receivers with mechanical source of power; paper-feeding arrangements for receivers; repeating systems employing contact-making relays; perforated strip transmitters; distributor systems. - Relates to synchronized cable-code or like transmitters and retransmitters of the kind in which the character of the outgoing signals is determined by incoming signals or perforated tape, while their duration and timing is determined by independent means in synchronism with incoming signals. In the present apparatus the contact-actuating mechanism discontinues its reciprocating motion so long as only spacing signals are being received, and the magnitude of that motion is self-determined. In a simple form of the invention (Fig. 1, not shown), a contactactuating spring arm is swung, under the control of an electromagnet to which the signals are applied, within reach of a cam which can actuate it, so as to send on a signal. Retransmitter for cable work. A shaft 26, Fig. 2 (plan), synchronized with the incoming signals, carries a lower actuating-cam 5 and an upper restoring-cam 25. When the armature 11<a> is attracted by the dash magnet 3<a> the slide 10<a> carried by it is caught (by means of a hook formed on it, see 18, Fig. 3, not shown) by the cam 5 and dragged down so that its catch 21<a> turns the lever 19<a> about its pivot 22a, moving the contact 20<a> to the right. After an interval the lever 19<a> is restored to its leftward position by the cam 25. A duplicate set of apparatus is provided for actuating the dot contact 20<b>. Signals may be applied to the transmitter by strip-controlled mechanical means instead of by electromagnets 3a, 3b, Fig. 2; or the latter electromagnets may be controlled by perforated strip. Synchronous movements. The phase-relation between the incoming and outgoing signals is adjusted by rotation of the base 27, carrying the cam-actuated apparatus, about the cam-shaft 26, the speed of which may be controlled by the incoming signals as described in Specification 238,622. Jockey devices. The lever 19a, Fig. 2, may be held in position by a jockey wheel 24<a>, by magnet poles co-operating with a soft-iron tongue on the lever 19<a>, or by the device shown in Fig. 4, where a toggle member 29<a> is interposed between the jockey arm 23a and the end of the lever 19a which has to be positioned. Alternative forms of contact-actuating mechanism. In the modification shown in Fig. 5, the catch 32, when pulled forward by the magnet 3, is.caught by the cam 5 and turns the lever 80 about its pivot 31. The arm 35 then moves to the right, the ledge 36 slipping under the end 30<a> of the lever 30, and contacts located either at 39 or at 39<b> are closed. The catch 32 is eventually disengaged from the cam by the stop 33, and the arm 35 is restored by the cam 25. In the modification shown in Fig. 6, the armature 2, when attracted, does not have to move away from the magnet poles during the latching action of the cam. The catch 40 and armature 2. form a bell crank lever which is pivoted at 40<a> on a link 41 which is itself pivoted at 42. Diplex telegraphy; single battery for both polarities and for two transmitter channels with local recorders. The connections may be such (Fig. 7, not shown) as to enable the same battery to be used for both dot and dash signals. Fig. 8 shows a modification of the diplex circuit shown in Fig. 3 of Specification 292,281, wherein two pairs of contacts 20a, 20<b>, 120<a>, 120<b>, allocated to two different channels, serve a single outgoing circuit L, E. By means of equal bridging resistances r1, r2, the signals in the respective channels can be recorded separately by local recorders R1, R2. The manner in which the separation of the channels comes about is discussed in the Specification. Adaptation to special code. The apparatus may be adapted as shown in Fig. 10, to transmit the code described in Specification 294,715, wherein a dot is represented by (+ +), a dash by (- -), and a space by (+ -). The dot and the dash magnets are energized under the control of a tape perforated in ordinary cable code, but the parts actuated by the cams 5, 25 are so arranged that the contacts operate half a period later for dot signals than for dash signals. So long as spaces are being sent, the additional contact 51, reciprocated by the cam 50, sends signals of the form (+ -) to the line L, E through a circuit comprising the contacts 45<a>, 45<b>. For a dot signal the contact 20<b> moves to the left immediately before the contact 51, cutting out that contact and sending a positive impulse direct from battery to line via contact 39<b>, thus completing the (+ +) signal. For a dash signal the contact 20<a> is moved to the right at the beginning of the signal period, so that a (- signal is sent to line. At the receiver, Fig. 11, signals originating as a cable-code message a, Fig. 12, and transmitted as described in Specification 294,715, actuate the receiver dot contact 20<b>, Fig. 11, half a period late in accordance with curve b, Fig. 13, while they actuate the receiver dash magnet 20<a> in phase in accordance with curve c. The resultant potential drop in the resistance P is shown by curve d, Fig. 14, and owing to the intermittent interruptions of the contact 55 the signals registered by the instrument R are of the form e, Fig. 15, which corresponds to the original form a. Translating from one code to another; tape-feed mechanism. Apparatus for translating from one code to another is described in the preceding and following paragraphs of this abridgment. Further, the cable-code transmitter shown in Fig. 2 may be operated by tape punched with the Wheatstone code, in the manner described in Specification 26278/13. The perforated tape may be fed step by step at the rate of one hole for each dot or space and two for each dash : or the feed mechanism described in Specification 26278/13 may be modified so that the tape is fed continuously, an extra step of one hole being imposed for each dash. Perforated-tape recorders. - The output from the apparatus shown in Fig. 2 may be used (Fig. 9, not shown) for punching tape fed forward in response to current impulses controlled by the shaft 26, the punches being operated by the output currents or directly from parts corresponding to either 10<a> or 19<a>. Wheatstone tape may be formed, the dot and dash punches being each adapted to punch two holes in the required positions while the feed may be controlled as described in Specification 28952/13.