Patent GB-172105-A (GB)
Title: Improvements in and relating to telegraphic receiving and transmitting apparatus
IPC: H04L25/04
Filed: 1920-08-30
Abstract: 172,105. Marks, E. C. R., (Horn, J. A. L.). Aug. 30, 1920. Restoring or modifying imperfect signals; systems using code elements distinguished by duration or polarity of current; synchronous movements. - In apparatus for receiving, correcting, and storing signals and subsequently, if desired, re-transmitting them, of the kind in which signals displace pins laterally on a moving member, the moving member is in the form of an intermittently moving chain carrying pins which are movable laterally in either direction according to which of two local circuits is completed by the signals received. In an example, the chain consists of thin steel plates, Figs. 4 and 5, held together by rivets 2. Pins 4 fit loosely on the holes 3, and each has a weak spring 5, with a turn at each end of smaller diameter than the pin, to hold it in any position to which it is displaced. The links are reduced at the ends as shown and held together by the pins. The chain 8 passes round a receiving wheel comprising two discs 9, 10 with notches as shown, Figs. 2 and 3. Ratchet wheels 13, 14 having as many teeth as there are notches on the discs 9, 10, and arranged so that one is half a tooth in advance of the other, are fixed to the receiving wheel. The spindle 12 of the receiving wheel is frictionally driven by the clutch levers 17, 18, Fig. 3. The ratchets 13, 14 engage pawls 25, 26 controlled by the armatures 30, 31, of the feed magnets 33, 34, one of which is actuated at the beginning and end of each signal impulse. The marking-magnet 38 actuates the thrust rod 40, whose end is nearly twice the width of a pin. The spacing-magnet 48 similarly actuates the thrust rod 49, which is half the width of a pin, away from the rod 40 in the direction of rotation of the receiving wheel. Means for allowing rotation of the receiving wheel when signals are not being received and during dashes. On a spindle 55, Figs. 1 and 2, are fixed four discs 56-59 each with a cam, 90‹ from the seat. A fifth disc 61 on the spindle 55 has four cams 90‹ apart. Four levers such as 63, pivoted round the pin 67 and normally pressed towards the discs 56-59 by spring 70 can be held in their outward position by engagement with the levers such as 71 as shown by the full lines in Fig. 2. The levers 71 &c. are lifted clear.by the pin 77 when the armature 78 of the magnet 52 is attracted. A bell-crank lever 80, pivoted at 81, is pulled counterclockwise by a spring 82. If one of the levers 63 &c. is in its inward position it encounters the projection 83 of the levers 80 and prevents its movement. When all the levers 63 &c. are in their outward position, a further movement of lever 80 allows the extension 84 to encounter the cam wheel 61. Simultaneously the hook 86 will depress the ends of the levers 71 &c., releasing the levers 63 &c. Owing to the speed of rotation of the cam wheel 61, 1000-2000 revolutions per minute, the extension 84 receives a sharp blow and its inertia carries it clear of the cam-wheel. This movement is transmitted by the rod 87 to the lever 89, pivoted at 90, which by means of the pin 91 disengages whichever of the pawls 25, 26 is in engagement with a receiving wheel ratchet. The spindle 55 is coupled direct to a direct-current shunt-wound motor, and rotates counterclockwise. It is geared to the clutch spindle 24 so that if unimpeded, the receiving wheel would move the distance between two pins, while the spindle 55 makes one-eighth or less of a revolution. Thus for each revolution of the spindle 55, the receiving wheel moves forward one tooth. By means of an adjustable resistance in the winding of the motor, the spindle 55 makes approximately one revolution for each centre hole in the tape passing the transmitter. Operation by long and short signal impulses. As shown in Fig. 6, the magnets 38, 34 and 48, 33 are in series. On receipt of a dot, the tongue of relay 50 moves over to its positive contact and magnets 38, 34 are energized. The thrust-rod 40 displaces a pin and is lifted clear through the action of the rod 42 just before the armature 39 completes its travel. Meanwhile armature 31 of magnet 34 depresses pawl 26 and allows the receiving wheel to rotate half a tooth. On the return of the tongue of line relay 50 to its negative contact, the thrustrod 49 is thrown forward but does not displace a pin since it is resting on top of the pin already displaced. Simultaneously the pawl 25 is depressed and the pawl 26 released, allowing a further rotation of half a tooth. At the beginning and end of the dot, the magnet 52 is energized ::momentarily, causing the levers 71 &c. to free the levers 63 &c. so as to prevent release of the receiving wheel by the action of the lever 80 until a further revolution of spindle 55 has taken place. When a dash is received, the marking current displaces a pin as in the case of a slot, -but as its duration allows more than one revolution of spindle 55, lever 80 is released, and operates detents 25, 26 as described above to allow the receiving wheel to move forward one tooth, so that on arrival of the spacing current, the thrust rod 49, being clear of the pin already displaced, will displace a second pin. Continuance of the spacing current allows further rotation of the receiving wheel without the displacement of pins, through the action of the lever 80. The release of lever 80 takes place at the earliest threequarters of a revolution of spindle 55 and at the latest a complete revolution after the freeing of the levers 63 &c. The shaded portions in diagram 7 of Fig. 5 shows the margin during which lever 80 is released. Signals may be received within this limit even if distorted, and recorded correctly. By increasing the number of cams the margin may be increased. Re-transmitting apparatus. The repeating wheel 92<a>, Fig. 2, is of similar construction to the receiving wheel but has no ratchets. It is fixed to a shaft 92b, geared to the shaft 55 so that for each revolution of the latter the wheel moves forward the distance between two pins. Fixed to a spindle 93 are two levers 94, 95 of the shape shown in Fig. 9, and a third lever 96 carrying an insulated contact spring 98. A spring 99 presses the levers 94, 95 downward and keeps the spring 98 in contact with the spacing contact screw 100. Displaced pins engage one or other of the levers 94, 95 and cause by the operation of lever 96 and contact spring 98 marking currents of appropriate duration to be sent to line. When the pins have operated the levers they are returned to the mid-position by the wedge pieces 102, Fig. 1, or by means of toothed wheels as shown in Fig. 10. The repeating wheel can be made to operate a printer or tape perforator in place of relaying signals to line. Operation by positive and negative signal impulses. In a modified apparatus for use with a code in which dots and dashes are distinguished by using currents of opposite polarity, the thrust rods 40, 49, Fig. 11, are arranged directly opposite one another. The receiving wheel has only one ratchet wheel and an escapement of the form shown. On the spindle 55 is frictionally mounted a disc 113, Fig.' 12, with two opposite notches. A lever 115 provided with a hook normally prevents its rotation. The lever 115 carries a contact spring 116 co-operating with contacts 117, 118 according to whether the lever is in or out of the notches in the disc 113. A bell-crank lever 119 pivoted at 120 has a pin 121 extending across the levers 63 &c. and carries two contact springs which complete the contacts 122<a>, 122b when all the levers 63 &c. are locked in their outward position by the levers 71 &c. Fig. 16 shows signals on a tape 131 and recorder 132 and the corresponding displaced pins in a chain 133 representing the letters L.N. Circuit arrangements for this modification are shown in Fig. 15. When the dot 134 is received, the tongue of relay 124 goes over to its positive contact, energizing magnets 38, 52, and charging condenser 125. The pin 135 is displaced and magnet 52 releases levers 63 &c. and lifts lever 115, causing contact spring 116 to touch contact 118 and discharge condenser 129. Disc 113 makes half a revolution when lever 115 stops it and contact spring 116 touches contact 117, operating magnet 112, and allowing the receiving wheel to escape one tooth. This delayed escapement allows signals to be correctly received even if they arrive somewhat late. The following dash signal similarly actuates magnets 48, 52 and the pin 136 is displaced. Of the remaining two dots the first will be received in the manner described, the second will actuate magnets 38, 52 only when the contact 122 &c. is made, about one revolution of spindle 55 after the previous dot. If no signal arrives, the spindle 55 causes contact 122 &c. to be made once per revolution, thus releasing levers 71 &c. and 115 and allowing receiving wheel to escape one tooth. It will make no essential difference if the dots and dashes are run together. The shaded portions in Fig. 16 indicate the period during which a signal may arrive to be correctly recorded. The repeating wheel is similarly constructed, but the levers corresponding to the levers 94, 95 shown in Fig. 2 are equal in size and move independently, actuating separate contacts to put positive or negative battery to line. Synchronizing repeating and receiving wheels. The chain 8, Fig. 2, passes under a roller 104 on the end of a pivoted arm, and forced downward by a spring 107. A contact spring 106 is moved to contacts 108, 109 according to the tension of the chain. By means of the connections shown in Fig. 8 a small motor 110 is thus actuated one way or the other to put more or less resistance on to the shunt winding circuit of the motor driving the spindle 55.