Patent GB-190223842-A (GB)
Title: Improvements in Electric Telegraphy.
Inventor: HESSE FREDERICK EDWARD
Filed: 1902-10-31
Granted: 1903-10-29
Abstract: 23,842. Hesse, F. E., and Heurtley, E. S. Oct. 31. Telegraphs.-Relates to means for translating from one cable to another. The tongue of a moving coil or other receiving-instrument moves in close proximity to a conducting-surface divided into three divisions insulated from one another. The air gap between the tongue and the conducting-surface is in the secondary circuit of an induction coil, and, when the tongue moves away from the neutral position over one or other of the lateral conducting-sections, the sparks pass to that section, and the secondary current passes through the "dot " relay g, Fig. 2, or the " dash " relay h, as the case may be. When no current is passing, the tongues of the relays rest against their contact-stops g', h', and close the circuits of the battery m through the dot- and-dash relays k, l, the tongues of which are normally held against the contact-stops k<2>, l<2>. The relays k, l, instead of being worked directly, may be controlled from a differentially-wound neutraltongue relay, the coils of which are connected to the relays g, h. When one of the tongues g<1>, h<1> (say g<1>) is deflected, the symmetry is disturbed and a difference of potential set up between the wires g<3>, h<3>, a small current then passing through the resistance o, condensers p, p<1>, resistance o<1>, and main signalling-coil q, thus boosting up the current in the coil q and preventing it from falling to zero owing to the choking effect of the receiving-condensers r. The small current which passes through the relay k is insufficient to energize it, and its tongue falls against the contact-stops k<3>, thus completing the circuit of the sending - battery s throngh the cable t and earth e. The rate of rise of the boosting current may be regulated by high inductance instead of by capacity, and instead of passing the boosting current through the receiving- coil or a second coil wound on it, it may be used to energize electromagnets which co-operate with a polarized armature carried by the moving coil. The relay shown in Figs. 3 and 5 is preferably used in place of the ordinary relay. The polarized electromagnet M acts on a telephone diaphragm A, to which is attached an arm B carrying a piece of platinum wire C, the ends of which form the contacts. Two metal arms D, E pivoted at F, G are balanced so as to press against the wire C. When the intermittent or alternating current from the spark circuit passes through the coils of the magnet, the diaphragm vibrates more rapidly than the arms D, E can move, and the connection between them is broken. Electrostatic relays may be used instead of electromagnetic relays, two plates being drawn together by the high potential of the spark current. Instead of using receiving-condensers, the current may be curbed by means of two coils wound together and suspended in a magnetic field. One coil conveys the cable current to earth ; the other induces a current which is conveyed to the signal coil. Or the receiving-coil may be differential, in which case an induction or capacity shunt is provided in one winding of the coil. In the translating-device shown in Fig. 6 a neutral-tongue relay 1 is actuated by the spark relays, and a highresistance neutral-tongue relay 2 is used in conjunction with it. The transmitting or " key " relays are shown at k and l. A deviation of the tongue 1 to the left closes the circuit of the battery 3 through the shunted " delay magnet" 4, tongue 1, and " dot" relay k. At the same time a weak branch-current passes through the high-resistance relay 2 and " dash relay l. The relay l does not respond, but the relay 2 is energized, the tongue moving to the right and keeping the circuit of the relay k closed, independently of the relay 1, until the " delay magnet " 4 acts and breaks the battery circuit, thus sending a current of standard duration to the cable. If a letter such as S is signalled, the delay-magnet acts three times during the long contact made by the spark relay, and three separate dots are transmitted to the second cable. The retardation of the electromagnet 4 can also be produced by inductance, resistance, or capacity, or by mechanical means. When sending block signals (signals without individual beats on the same side of zero), the contact-breaker associated with the magnet 4 is placed in circuit with the coils of the relay 2, in which case the breaking up of a long signal into a succession of short ones does not take place, but its length is corrected by the action of the delay magnet. In both arrangements the second relay 2 may be dispensed with, an extra winding being placed on the coils of the relay 1 through which the local current passes, so that the tongue is held over until the delay magnet releases it. Better definition is obtained when sending block signals by placing a make-and-break contact between the transmitter and the cable, the cable being put alternately in circuit with the transmitter and with earth. The apparatus for doing this is shown diagrammatically in Fig. 8, in which k, l are the dot and dash transmitting relays, and L the cable. A constantly-revolving commutator 7, 8 is provided with three brushes 9, 10, 11, of which the last-mentioned is movable laterally so as to vary the relative intervals of connection of the cable to the battery at 9 and to earth at 10. When one of the relay tongues is actuated, the brush 9 is connected to one pole of the battery, and the other pole is earthed, but owing to the action of the commutator the cable is earthed for a certain proportion of the period during which the relay tongue is held down. The Provisional Specification states that a double commutator or contact-breaking device may be employed instead of the usual vibrating interrupter in the primary circuit of the induction coil, on part serving to make or break the primary circuit and the other to connect the tongue to and insulate it from the secondary circuit, thus getting a unidirectional secondary discharge. The Provisional Specification also describes a method of primary transmission, in which the automatic transmitter works through two polarized relays, which earth the cable after sending a signal and send a current of opposite sign into the cable in the long period between two letters.