Patent GB-296811-A (GB)
Title: Improvements in or relating to telegraph systems
IPC: H04L5/22
Filed: 1927-06-09
Abstract: 296,811. Beatty, W. E. June 9, 1927. Type-printing telegraphs; distributor systems; eliminating effects of disturbing currents. - In a printing- telegraph system of the kind employing combinations of five impulses of two polarities, local subsidiary records of the impulses are obtained by connecting siphon recorders in shunt with the transmitter contacts, the local retransmitter relays, and the receiver selector magnets. In orrder, as described in Specification 9666/14, to prevent wandering of zero due to a preponderance of impulses of one polarity, the polarities of marking and spacing impulses are interchanged by the transmitter at the end of every five-impulse combination except one, and by the local retransmitter after the second impulse of each combination, so that the normal polarities inverted for 13 out of the 25 impulses comprised in five signal channels. Transmitter. In Fig. 1 the + and - signs indicate the polarities of the impulses sent to line 107 on the assumption that these are all spacing impulses, the movable contacts of the. tape transmitters A - - E being all shown in the lefthand position; thus the transmitters B. D, are connected to the + and - mains 109 in reverse as compared with the transmitters A, C, E. The distributor brush 108 connects the transmitting segments 101<a> successively to line 107 through the ring 101<b> and switch 111, and at the same time to local siphon recorders 102 - - 106 through segments 101<c>, yielding a local record of the outgoing signal. Local retransmitter. The short line 107 leads through switch 216, Fig. 2, to a line relay 201 controlling a retransmitter which reverses the polarities of spacing and marking signals, as received from the transmitter, Fig. 1, after the second impulse of every five-impulse combination. The relay 201 distributes impulses. similar to those received from the line 107, through brush 202 and segments 203a to relays 204 - - - 208 in succession, these relays being common to all five channels and corresponding to the five impulses of each combination. Their armatures are connected to the segments 210a in multiple, so that + or - currents from the battery 218 are distributed by the brush 219 to local records 211 - - 215 through segments 210<c> and are also sent to the cable 209 through ring 210<b>, network 221, and switch 227. The fixed contacts of relays 204, 205 are connected to the battery poles 218 in the order revere to that of the fixed contacts of relays 206, 207, 208, so that where the incoming currents are of the polarities marked on ring 101<c>. Fig. 1, the outgoing currents will be as marked on ring 210<a>, Fig. 2. Receiver. Signals from the cable 209, Fig. 3. are passed through switch 309<a>, amplifier 320 and vibrating relay circuit 321 to the relay 301 which repeats the received signals to the distributor. The armature of the relay 301 is connected to the ring 302<b> of the distributor, so that + and - impulses as received are distributed through the brush 303 and contacts 302<c> to the local siphon recorders 304 - - 308, which are differentially arranged as described below so that they yield a record free from the reversals in meaning of the impulse polarities which were introduced by the transmitter and retransmitter. The selector magnets 322 of the five printers F - - K are arranged to operate in response to marking currents of the polarities indicated in Fig. 3; these polarities are therefore opposite to the spacing polarities shown at 210<c>, Fig. 2. As a safeguard against false actuation the magnets 322 are permanently connected to the appropriate poles of the battery 310; they are in turn connected through segments 302a and ring 302b to the armature 301<a>, so that their terminals are connected either to the same or to opposite poles of the battery 310. The polarities to which the respective selector magnets 322 are responsive are so chosen as to eliminate, the effects of the reversals in polarity-meaning introduced into the line signals. Differential circuit for siphon recorders.- The siphon recorders 211 - - 215, Fig. 2, and 304 - - 308, Fig. 3, are so arranged that a + impulse applied to terminal A has the same effect as a - impulse applied to terminal B, and vice versa. Thus the siphon pen records above or below the line according to the polarity of the current passing in one direction through the instrument; a + current at terminal A divides itself between resistance 224 and the recorder, passing to earth at C. Similarly a - current at terminal B divides itself between resistance 223 and the recorder, through which it passes in the opposite direction so as to produce the same effect as that of a + current applied to terminal A. Two way working. The transmitter, Fig. 1, is associated with a receiver 112, and the receiver, Fig. 3, is associated with a retransmitter and transmitter 319. The arrangement is not duplexed and for up-and-down working the direction of traffic is reversed at stated intervals by time switches operated by cams 111, 216, 225, 314, 317. The arrangement is such that the amplifiers 226, 320, which are preferably of the hind described in Specification 258,614, come into play only for received signals.