Patent GB-287229-A (GB)
Title: Improvements in or relating to diplex and multiplex telegraphy
IPC: H04L25/20
Filed: 1926-12-16
Abstract: 287,229. Higgitt, H. V., and Eastern Telegraph Co., Ltd. Dec. 16, 1926. Restoring or modifying imperfect signals; repeating systems using contact-making relays; distributor systems; perforated strip recorders. - Relates to systems of the kind described in Specifications 234,179 and 238,622, for transmitting or relaying signal impulses and comprises means enabling the system to be used for multiplex signalling in channels whose speeds differ. As shown in Fig. 7 (Comp.), a hammer 20 is reciprocated by a cam 19 and either engages or misses the interposed piece 5 according as the magnet 3 is or is not energized by a signal received from the tape, if the apparatus is a transmitter, or from the line in the case of a retransmitter or receiver; one such device controls the emission of dot signals through the contact 21, and another the emission of dash signals through a second similar contact. According to the present Specification the system is adapted for diplex channels of unequal speed, the cams being so designed that the signals of each channel are uniformly timed before and after transmission, while during transmission their timing is disturbed so that they fit together into a uniformly timed aggregate. Thus if impulses a1, a2, in the high-speed channel be interspersed with impulses b in a channel of half their speed, in the order a1, a2, b, a1, a2. b - - -, a cam for the faster channel a1, a2 is designed as shown in Fig. 1 (Prov.)]; whenever incoming impulses occur in that channel they do so at points a1, a2, which are 120‹ apart. The hump 31 immediately engages and presses home the hammer 20, but the hump 32 is so shaped that while it immediately causes the hammer 20 to engage or select the piece 5, it does not press the piece home till the point A2 is reached. Thus the signals retransmitted at A1, A2, are equally spaced. The point b indicates the phase of the signals in the second channel, which are retransmitted by a separate cam. The inverse operation is performed at the sending end of the line by a cam shaped as shown in Fig. 2 (Prov.); dot and dash signals from the automatic transmitter are applied to the magnets 3, 4, respectively and occur at the equidistant points a1, a2, the outgoing signals being selected accordingly at those points but transmitted at the unequallv spaced points A1, A2. A second cam effects the transmission of signals in the slower channel at the point B, or the two cams may be combined, Fig 3 (Prov., not shown). The system may be used for punching strip instead of transmitting, the hammers and interposed pieces being then designed as shown in Fig. 7 of Specification 28952/13. The present Specification also describes cams suitable for two channels whose speeds are in the ratio 3:2. the order of the signals being a1, a2, b1, a3, b2 repeated (Figs. 4'-- 8, Prov., not shown). With three channels having speed ratios 4 : 2 : 1 three cams are used and the order of signals is a1, b1, a2, c, a3, b2, a4; with speed ratios 4 : 3: 1 it is a1, b1, a2, b2, a3, b3, a4, c, and in this case the a cam may have one hump and rotate four times per cycle. The invention also provides for the case where an intermediate station is used sometimes for retransmitting and sometimes for originating messages in two channels of speed ratio 2: 1. When retransmission is taking place the impulses in the faster channel are received and retransmitted at irregular intervals as indicated by the humps a1A1, a2A2, in the appropriate cam, Fig. 1 (Prov.), but when signals are to be originated at this station the controlling magnets 3, 4, Fig. 8 (Comp.), are disconnected from the " in " line and connected to a local transmitter in lieu; and at the same time a cam shaped as in Fig. 2 (Prov.), is slid into the place of the cam in Fig. 1 (Prov.). Alternatively, a detachable piece 35, Fig. 4 (Comp.), may be added to the hump a1A1, Fig. 1 (Prov.). On the other hand, when an intermediate station is to be used sometimes for receiving and sometimes for retransmitting, the cam for receiving is shaped as in Fig. 1 (Prov.), but this can be converted for use in retransmitting by the addition of a piece 36, Fig. 6 (Comp.). The duration of the " out " impulses may be determined by latches and tripping cams as described in Specification 234,179, and the tripping cams appropriate to receiving or retransmitting are changed at the same time as the cams shown. Specification 265,806 also is referred to.