Patent GB-245175-A (GB)
Title: Improvements in synchronous telegraph systems
IPC: H04L7/00
Filed: 1924-07-30
Abstract: 245,175. Marks, E. C. R., (Morkrum Co.). July 30, 1924. Synchronous movements and synchronism indicators; duplex and quadruplex telegraphy; distributor systems.-Relates to synchronous telegraph systems of the type in which the distributors of connected stations are each driven by a motor controlled by a vibratory member, and in which one of the distributors automatically receives an intermittent correction of predetermined value. According to the invention, the corrected distributor also receives a continuously applied automatic correction of variable value. Parts 1 and' 2 of Fig. 1 respectively show the receiving and transmitting arrangements at one station of a printing telegraph system, the second station, connected to the first by the line L, or operated by wireless control, being, similarly equipped. The transmitting and receiving distributors are independently driven, each by its own motor C or G, the speed of which is governed by an electricallymaintained fork 45 or 45<1> in the manner described in Specification 245,404, [Class 38 (iii), Electric motor control systems &c.]. The speed of the receiving distributor continually varies, always tending to be either slightly above or slightly below that of the transmitter, but its mean speed is maintained at the proper value by the automatic corrections effected by the transmitted .signals. The system is designed for Baudot code signalling, and is shown as arranged for diplexduplex operation. Transmitting arrangements. In the tranismitting distributor (Fig. 1, Part 2), the first contacts 10 transmit impulses to segments 17 of the distributor from supply conductors 11 or 12 according as they are shifted into contact with either lead 13 or lead 14. A similar set of contacts (not shown) for the second channel are connected to segments 17<1>. Magnets such as 24, energized when a brush 23 in the distributor engages segments 21, 21<1>, control the key-board or tape-feeding mechanism associated with each set of transmitter contacts. The signal impulses pass through a conductor 20 to a local line relay LR, Fig. 1, Part 1, one winding of which is connected to the line L and the other to an artificial line 50. Thus each line relay responds only to impulses imparted to the line from the distant station. Receiving. The receiving distributor comprises three brushes rotating over segmental and annular contacts arranged concentrically. Each brush spans two rings, as shown in Fig. 2, and the set of segments 108, 110, which serve for the automatic correction at the rate of the controlling- fork 45<1>, is adjustable relatively to the other sets of contacts. The receiving contacts 55, 62 are arranged in pairs alternately connected together and to one or other side of a " printer relay " PR, the tongue 54 of which moves over with each movement of the tongue of the line relay LR. A contact 58 is associated with each contact 55 or 62, and is connected to one of a number of magnets 51. The arrangement is such that when the receiving distributor is in phase with the transmitter, if the transmitting contacts 10 are in their normal positions (as shown in Fig. 1, Part 2) no current will pass through the receiving magnets 51, but any one of these magnets is energized when the corresponding transmitter contact is shifted to its " alternate " position. A printer operating magnet such as 64 is associated with each set of receiving magnets, and is energized at the proper instant when the brush 66 engages one of a pair of contacts 65, 65<1>. Controlling speed of receiving distributor. The fork 45<1>, which controls the motor G driving the receiving distributor, vibrates in the field of two electromagnets, one of which, 74, preferably has two windings arranged above and below the tines of the fork, Fig. 6; the other magnet 88 is adjusta'bly mounted with its poles in alignment with the tines. The magnet 74 is connected through a rheostat 77 and switch 82 to the tongue of a relay HR. The magnet 88 is connected through a switch 135 to a rheostat 1, the arm 9<1> of which is continually moved by a motor 101 in one direction or the other very slowly over the resistance 90, so that the current through the magnet 88 is always gradually increasing or diminishing. The direction of rotation of the motor 101 is dependent upon the position of the tongue of a relay MR; this relay and the relay HR are simultaneously controlled by a relay OR, the tongue of which periodically transmits positive impulses from contacts 119 on the distributor, and the coils of which are connected to a relay SR associated with a series of " correcting segments " 108, 110 in the distributor. Alternate pairs of these segments are connected together, one set 110 being connected through a condenser 112 to the tongue of the relay SR, and the other set 108 being connected to one coil of this relay. A contact ring 115, over which moves the brush 116 coacting with the segments 108, 110, is connected to the tongue of the line'relay LR. During the ordinary working of the system, the switch 135 is closed and the switch arm 82 lies in the lefthand position. The tongues 80, 107 of the relays HR, MR normally lie in the positions shown, so that no current flows through the magnet 74 and the motor 101 runs in such a direction that the rheostat arm 91 gradually decreases the current through the magnet 88. Under these conditions the receiving distributor gradually lags behind the transmitter with the result, eventually, that by the operation of line impulses acting through the correcting contacts 110 and by the consequential operation of the relays SR, CR, the tongues of the relays MR, HR are moved over to the left-hand positions. This brings the magnet 74 into action, to speed up the vibrating fork, and at the same time the motor 101 is reversed and so brings about an increase of current in the magnet 88. When by the simultaneous action of the two magnets synchronism has been restored, the tongues of the relays HR, MR again take up their original positions. In starting the working of the system, the relative speeds of the correcting and corrected distributors are first determined. This is done by means of lamps S, F respectively connected to two sets of contacts 70, 72 in the distributor, the arrangement being such that when a switch 61 (closed during normal working of the system) is opened, both lamps are lighted together if the transmitting and receiving distributors are in synchronism. If the receiver is running fast or slow, the lamps are extinguished in definite order, and the condition existing is determined by noting what effect occurs. The magnet 88 may be controlled manually by the switch 135, which is adapted to connect it to a battery 136. A switch 87 is also provided to short-circuit a resistance 75 in series with the magnet 74, when it is necessary, after the initial speed adjustments have been made, in starting the working of the system, to speed up the receiving distributor temporarily to bring it into proper phase with the transmitter.