Patent GB-191409718-A (GB)
Title: An Improved Electro-mechanical Selector.
Inventor: GODFREE ERNEST GRAHAM
IPC: H04Q5/16
Filed: 1914-04-20
Granted: 1915-07-08
Abstract: 9718. Godfree, E. G. April 20. Party-line systems.-In systems of the kind in which each station can call any other station on the same line, other stations being locked out, the apparatus is so constructed that the necessary operations at the calling station must be effected in the proper order. The talking circuit at the calling station is closed by the depression of a sliding member, which can only be depressed.when the receiver is removed from its hook, and then operates to lock the dial of the impulse-sender, to release the impulsesending mechanism, and then to lock this mechanism to prevent further impulses being sent to line. If an attempt is made to call when the line is engaged, the sliding member is locked against depression by the armature of a polarized relay, and a lamp lights up. Operations at calling station. Fig. 8 shows the circuits of one station, and Fig. 7 part of the line connexions for three stations. When the receiver is removed from the hook 4, a lever 6, Fig. 5, rocks to close contacts 5, 7, 9 and 11, 13, and also uncovers a hole 14 in the casing so as to allow the depression of the sliding button. The closure of contacts 5 7, 9 completes a circuit over which a preliminary impulse is sent to line from earth c at the calling station, over contacts 32, 66, battery d, contacts 5, 7, 9, 116, line a to polarized relay 56<1>, Fig. 7. This relay connects battery g to line to energize relays 56, which, as shown in Fig. 4, close contacts 66 and open contacts 64. When the number-sender 46 has been set to call the wanted station, the button 16 is depressed. The edge 17 of this button, as shown in Fig. 6, acts on the end 12 of the arm 6, pushes it over and locks it in position by its engaging with the groove 28. The end of the plug also moves spring 38 from contact 41 to contact 40, and the block 30 on the plug closes contact 29, Fig. 2. The depression of the plug also allows an arm 42, Figs. 2 and 3, to fall past a projection 48 on the plug, thus allowing the arm 50, Fig. 3, to lock the impulsesender dial 46, and allowing a further movement of the hook-switch arm, as the rod 43 attached to this arm works in a slot 52 on the arm 42. The further movement of the hook switch causes the pin 22 to open contacts 32, thus breaking the circuit through the magnets 56<1>. The dial 46 carries a pawl 78 which rotates round the ratchet disk 80 and engages with a notch corresponding to the desired station. The movement of the dial 46 also winds up the driving-spring 74; but the ratchet disk 80 and the gear-wheel 86, which is on the same shaft, are normally held by the arm 90, Fig. 3. When the plug 16 is depressed, however, the projection 48 on the plug acts on the extension 94 of the arm 90 to release the arm from the studs 88, and the impulse mechanism thereupon returns to normal position. The wheel 86 gears with a pinion 100 on the shaft 104<a>, which carries a contact-making cam 106 to operate the springs 114, 116. The spindles 104<a> also carries a wheel 108 which gears through a worm 110 with a braking-mechanism. The armature of the magnet 56 carries an arm 60 which engages a catch 62 on the plug 16 to prevent the depression of the plug if the magnets 56 have been energized by another calling station. Selecting - mechanism at receiving - station. The impulses are received by the magnet 120, Fig. 4, and the pawl 126 drives the ratchetwheel 122. When the impulses cease, the pawl at the desired station rests in the shallow tooth 124, the member 136 engages the spring 138, and the extension 130 engages with the contact 132, thus ringing the bell in the manner described in Specification 10,706/10. General operation of the system. When the number-sender operates the contacts 114, 116, Fig. 8, at the calling station, impulses are sent to line from earth c over contacts 114, battery d, contact 116 to line a, and to polarized relay 56<1>. Fig. 7. This relay sends the impulses over the line to the line relays 56, which repeat them to the magnets 120. The bell circuit at the called station is from battery d over contacts 5, 11, bell h, contacts 132, 64. When the receiver is removed at this station the transmitter circuit is from battery d over contacts 5, 7, transmitter 22, induction coil j, contacts 132, 64. The receiver circuit is from line f over condenser i, receiver k23, coil j, pawl 126, contacts 138, 7, 9, 116 to line a. At the calling station, the transmitter circuit is from battery d over contacts 5, 7, transmitter 22, coil j, and contacts 11, 13, 64; and the receiver circuit is from line f over condenser i, receiver k23, coil j, contacts 40, 38, 7, 9, 116 to line a. If a third subscriber takes down his receiver while the line is engaged, the lamp 72 is brought into a circuit from battery d over contacts 5, 7, 38, 41, 138, 11, 13, 64. When the connexion is released, and the plug at the calling station is returned to normal position, the contacts 30, 32 are simultaneously closed to send a reverse impulse to line to actuate the polarized relays 56 in the direction to remove the detent from the ratchet 122, Fig. 4, thus releasing all the selectors.