Patent GB-372749-A (GB)
Title: Improvements in or relating to telegraph systems and apparatus therefor
IPC: H04L17/00
Filed: 1931-02-05
Abstract: 372,749. Type-printing telegraphy. CREED & CO., Ltd., Telegraph Works, Croydon, Surrey.-(Teletype Corporation; 1400, Wrightwood Avenue, Chicago, U.S.A.) Feb. 5, 1931, No. 3655. [Class 40 (iii).] In a telegraph system employing combinations of marking and spacing impulses, successive spacing conditions are transmitted by impulses of opposite polarity, and marking conditions are obtained by reversing the polarity of the corresponding impulses. The marking impulses may be of positive or negative polarity, but when occurring successively will be represented by impulses of opposite polarity. The rate of impulse distribution to the line is controlled by a tuning fork 1 whose tines 3, 4 carry members 7, 8 which in their outer positions complete the circuit of a driving magnet 13 to maintain the rate of vibration of the fork. In accordance with the perforations in a tape, a contact member 41, actuated between contacts 36, 37, controls through the contacts 26 .. 29, associated with the fork, the operation of polarized relays 23, 24 with tongues 21, 22 operating between contacts 42 .. 45 and effecting the transmission of impulses to the line 25 under control of contacts 17 .. 20 operated by the tine 3 of the fork at its outer and inner positions. With the tongue 41 in the spacing position (as shown) the tines 3, 4 in their outer positions effect the impulse transmission from tongue 21 over the contacts 17, 18, and over contacts 28, 29 energize a stepping magnet 31 operating an escapement through which the tongue 41 is positioned in accord with the tape perforations for the next impulse. Simultaneously a circuit is completed over tongue 41 for the relay 24 which is energized to move its armature in accordance with the next impulse to be transmitted. On the assumption that the second perforation represents a spacing condition, the relay tongues 21, 22 remain as shown and when the tines 3, 4 reach their inner positions an impulse of opposite polarity is transmitted from the tongue 22 over the contacts 19, 20 to the line 25. At the same time the circuit of the magnet 31 is closed, and the cam shaft 40 being stepped to set the tongue 41 for the next impulse, a circuit for the relay 23 is closed in accordance with the tape perforation. In the case of a marking condition the tongue 21 is moved to contact 42 and as the tine 3 reaches its outer position a reversed polarity impulse is transmitted over tongue 21 and contact 42. At the receiving end the impulses are applied to a polarized line relay 51 controlling further polarized relays 60, 61. With the receiving and transmitting forks in synchronism, during the reception of successive spacing impulses the tine 82 of the fork 83 moves in phase and synchronism with the tongues 53, 62, 91. During successive spacing conditions the tongues 53, 62 will be on their left-hand contacts as the tine 82 in its outward movement closes contacts 67, 69, and the circuit of the selecting magnet 72 of the receiving apparatus will be open at contact 64. Similarly at the inward movement of the tine 82 the tongue 62 will be on the contact 64, but as the contacts 68, 70 are closed, the circuit of the selecting magnet 72 is now open at the contact 63. At the outer and inner positions of the tine 82 a circuit through a battery 78 and an escapement magnet 75 is completed at the contacts 80, 80<1>. When a marking condition is being received the tongue 62 will be on contacts 64, 63 as the tine 82 reaches its outer and inner positions respectively, and in either case the selecting magnet 72 will be energized, and will move a cam shaft 74 longitudinally to operate a corresponding selecting finger. Synchronizing arrangements. The receiving fork 83 is arranged to vibrate at approximately the frequency of the fork 1, and is maintained in synchronism by the impulses representing spacing conditions. During a spacing condition, the tongue 91 of relay 60 and the tine 84 will be opposite in phase so that when contacts 87, 89 are closed, a circuit will be closed through battery 92, condenser 92 and contact 98 energizing magnets 96 ; in the inner position of the tine 84 with contacts 86, 88 operated the magnet 93 will be energized over the contact 95 of relay 40. During the reception of marking impulses the circuits of the magnets will be open at contacts 95, 98 at the inner and outer positions respectively of the tine 84 and no maintaining force will be applied to the fork. For reception, the tuning fork 83 is normally started by hand and spacing conditions are transmitted to the tine. Until the receiving fork falls into step, the fork vibrations die down and gradually fall into the correct phase relationship, when the magnets 93, 96 become operative as above described to drive the fork in synchronism. Transmitter. The transmitter operates so that the usual start-stop impulses are omitted and the tape is moved forward in preparation for the transmission of a second set of impulses whilst the final impulse of the preceding combination is being transmitted. The tongue 41, normally held against the contact 37 by a spring 99, is moved against the contact 36 in accordance with the perforations in the tape 118. Five bars 102 .., mounted on a spindle 103, extend across a plate 100 attached to the tongue 41, individually terminate in a raised portion 106, and are connected to five fingers of which only the fifth member 112 is shown. Mounted on a shaft 40 controlled by the escapement magnet 31, are five cams arranged so that the raised portions 106 may in succession drop into depressions 117 and raise the fingers into contact with the tape 118 under the action of springs 104, 105 ... If a perforation exists above the corresponding finger, the forward end of the corresponding bar moves downward sufficiently to actuate the member 41 to the opposite contact 36. Simultaneously with the engagement of the rod 102 with its cam depression 117 for the setting of the fifth finger 112, a roller 133 drops into a depression in a separate cam member on the shaft 40 and through a bell crank lever 130 moves a member 128 to step forward a ratchet wheel 121 secured to the shaft of the tape wheel 119. If the final impulse of a signal is a marking condition, the finger 112 is moved with the tape in an elongated slot 115 formed in the guide plates 113, 114 and on disengagement from the tape is returned to its normal position by a spring 116. The cam shaft 40 is driven from gearing 151 through a friction clutch 152 and through a slidable sleeve 138 engaging a pin 136 and formed with a tooth 147 engaging a notch 148 in a member 149 mounted on the shaft 150. To stop the transmission a member 140, carried on a lever 144, is lowered into a helical groove on the sleeve 138 which is moved to the right against a spring 139<1>, and is arranged to be disengaged from the shaft 150 at the termination of the transmission of an impulse combination. Receiver arrangements. The selecting and printing mechanisms are similar to those described in Specifications 218,643 and 220,280, [both in Class 40 (iii), Telegraphs, Electric], except for modifications consequent upon the omission of the stop impulses and of the interval allotted for the transfer of the selective setting of the five bars 179 .. (of which only the bar 179 is shown) to the printing mechanism. During the interval allotted to the reception of an impulse the shaft 74 is rotated a step under control of the escapement magnet 75, and when a marking impulse is received the shaft 74 is moved longitudinally under control of the magnet 72 so that a corresponding cam pin 166 .. 170 engages an associated selector finger 174 .. 178 which is set with respect to the appropriate actuating bar 179 .. When the fifth impulse has set the finger 178, a bellcrank 187, 188 rotates clockwise so that the bars 179 .. which are not latched by the corresponding fingers 174 .. 178 are moved to the right under spring action, and the corresponding bar 185 of the printing mechanism is lowered into the aligned slots. On the movement of the bell-crank 187, 188, a pivoted latch member 192 is released to engage a notch 190 in the bar 179, if that bar has not been moved to the right, to prevent its moving forward and affecting the printing operation if the setting of the finger 174 for the first impulse of the succeeding impulse combination is such as to unlatch the bar 179. After the printing operation has been effected, the bars 179 .. are returned to their normal left-hand positions, during the selective setting of the fingers 174 .. 178, by the rotation of the bell-crank 187, 188 in a counterclockwise direction. Specification 235,574, [Class 40 (iii), Telegraphs, Electric], is also referred to.