Patent GB-191315579-A (GB)
Title: Improvements in Automatic Telephone Exchanges.
Inventor: REEVES FRANK NORRIS
Filed: 1913-07-05
Granted: 1914-02-12
Abstract: 15,579. Reeves, F. N., and Lundell, A. E. July 5, 1912, [Convention date]. Automatic exchange systems. -Relates to ' satellite ' or sub-central systems in which subscribers are connected to sub-centrals, connected by trunks to their respective main offices, the object of the invention being to enable connexions between two subscribers on the same sub-central to be completed without the use of trunks to the main office. In the system described, a calling-line is connected by a preliminary selector to a connecting-circuit having associated therewith a set of register-controllers upon which the number of the wanted subscriber is registered in accordance with the number of impulses sent in by the calling subscriber. The out-going end of the connecting-circuit ends in a second preliminary selector, which is provided with two test wipers and two test relays, so that it can hunt over two sets of trunks, one set leading to the main office and the other set to local selectors and connectors. The test relay controlling the selection of inter-office trunks is normally operative, but when a connexion is required with a subscriber on the same subcentral as the calling subscriber, certain contacts on the registercontrollers complete the circuit of a relay, which substitutes the test-relay controlling the selection of trunks to local group selectors. Construction of register-controllers. Each unit consists of a shaft carrying a number of cams controlling contact springs as in the wellknown sequence-switch, but the shaft is set by ratchet mechanism 243, Fig. 2, responsive to the selecting-impulses sent in by the calling subscriber, and is returned to normal position by an escapement 246 controlled by a magnet 247. A second ratchet 249, and a star-wheel 252 are secured to a sleeve 250 loosely mounted on the shaft. The ratchet 249 is engaged by a pawl on a disk 262 rigid with the shaft. During the setting of the register the pawl passes freely over the ratchet 249, but during its return the pawl engages the ratchet, thus rotating the starwheel 252 so as to interrupt the contact 253, thereby transmitting impulses to operate the selectors. First preliminary selector. When a calling subscriber e<1>, Fig. 2, removes his receiver, his line relay 205 closes at contact 228 the circuit of the actuating-magnet 224, and at contact 209 prepares the circuit of the high-resistance winding of the cut-off relay 206, which energizes, as soon as an idle connecting-circuit is found, over brush 211, contact of release relay 396, Fig. 3, and relay 291. The cut-off relay 206 locks up over its low-resistance winding, disconnects the line relay 205 and actuating magnet 224, and extends the calling line over brushes 216, 217, wires 293, 294, Figs. 2, 3, and 4, normal contacts 423, 424, Fig. 4, of the second preliminary selector, wires 292, 295, Figs. 4, 3, and 2, to the register line relay 281. Operation of register-controllers by selecting- impulses. In the 100,000-line system described, each connecting - circuit is provided with five register - controllers 203, Fig. 2, 300, 301, 302, 303, Fig. 3, one for each digit. Associated with these is a timing-mechanism 241, Fig. 2, which produces a certain time interval between the restoration of successive registers, so as to allow time for trunk-hunting at the group selectors. A switching-device 240, Fig. 2, which controls the contacts shown above it and also the contacts 68, 290, Fig. 2, ensures a proper release in case the calling subscriber hangs up prematurely. The register line relay 281 closes the circuit of a slow-release relay 283, so that the first set of selecting-impulses is repeated over the back contact of relay 281 and the front contact of relay 283 through a slow-release relay 284 to the magnet 245 which sets the ' ten-thousands ' register 203. The relay 284 is energized by these impulses, and closes the circuit of a relay 286, which locks up over a circuit including a relay 285, which is at first short-circuited over the armature of relay 284, but, as soon as the impulses cease, is energized and extends a connexion from the left-hand armature of the relay 283 through the relay 284 and wire a to the stepping - magnet of the ' thousands ' register 300. The second set of impulses thus position the ' thousands ' register, after which the pair of relays 313, 314 energize in the same way as the relays 285, 286, thus extending the repeating-circuit to the stepping- magnet of the ' hundreds ' register 301. The ' hundreds,' ' tens,' and ' units ' registers are set in similar manner, being moved from their normal positions indicated by the references N to positions depending upon the value of the different digits in the wanted number. Selection of idle trunk to main exchange or to local selector. As soon as the ' tens ' register leaves its normal position, the starting-relay 427, Fig. 4, of the trunk finder is energized over wire 19, contact 336, Fig. 3, of the ' tens ' register 302, wire 18 to earth at the front contact of relay 283, Fig. 2. Assuming that the subscribers belonging to the same sub-central as the calling subscriber are numbered from 67,000-67,499 the ' ten-thousands,' ' thousands,' and ' hundreds ' registers are arranged to close their contacts 261, 360, 370 in positions 6, 7, and 0 to 4 respectively, and their alternate contacts 259, 364, 376 in all other positions. The trunk finder 400, Fig. 4, is provided with two test wipers 412, 413 connected to two test relays 425, 426, which respectively control the selection of an idle trunk such as 406, 407, 408 to the main exchange or of an idle trunk such as 403, 404, 405 to a local selector. If the registers are set to call a line on the same sub-central, the operative winding of the local test relay 426 is earthed over wire 341, contacts 370, 360, 261, wire 19, contact 336 of the ' tens ' register, wire 18, and the front contact of relay 283, Fig. 2. On the other hand, if the registers are set to call a line in the main office, the left-hand winding of the out-going test-relay 425 is earthed over wire 389, one or more of the contacts 376, 364, 259, wire 19, contact 336 to earth as before. The starting- relay 427 energizes the actuating-magnet 419 over the back contacts 433, 434 of the two test relays, one of which is energized when an idle trunk of the necessary set is found. The energized relay locks up over its low-resistance righthand winding, disconnects the magnet 419, and extends the talking circuit to the wipers 409, 411. If a local call is to be made, the relay 426 energizes a relay 322, Fig. 3, the function of which will appear later. Restoration of register controllers to normal position, and transmission of selecting-impulses. The talking circuit 372, 373 is at this time disconnected from the calling line at the contacts 381, 382 of the ' units ' register, but is bridged by a circuit including the interrupter contacts 371, 365, 375, 343, 253 of the different registers, and contacts 374, 399 in parallel. As soon as the trunk finder comes to rest, the interrupter 304 completes the circuit of a relay 321, Fig 3, over contact 325 and either the armature of relay 322 if the call is a local one or the armature of relay 425, Fig. 4, if the call is through the main exchange. The relay 321 prepares a circuit for a relay 319, which is energized as soon as a short-circuit over the interrupter 304 is removed. This arrangement of the relays 319, 321 ensures that the first impulse sent by the interrupter 304 over the wire 25 and contact 23, Fig. 2, to the escapement magnet 247 of the ' ten-thousands ' register shall be complete. During the return of the register 203, the star-wheel 252 interrupts the contact 253, until the register reaches its normal position in which the contact 23 is opened' and the lead 25 is connected over contact 26 to the stepping- magnet 31 of a timing device 241, which is rotated by impulses from the interrupter 304 so as to produce a certain time interval before the restoration of the next register. At its first movement, the device closes a contact 276, thus energizing a relay 287, so as to prepare a circuit for a relay 288, which is short-circuited by the contact 276 until this contact is again opened by the device 241. As soon as the relay 288 is energized, it connects the interrupter 304 over wires 25, 43, and contact 330, Fig. 3, to the escapement magnet 320 of the ' thousands ' register, which in returning to normal interrupts the contact 343, and then by closing contact 337 brings into action the timing device 241 to delav the restoration of the ' hundreds ' register. The relays 306, 307 act like the relays 287, 288 to extend the wire 25 to the escapement magnet of the ' hundreds ' register. The ' hundreds,' ' tens,' and ' units ' register are returned to normal similarly. These successive sets of impulses operate selectors at the main office in known manner. If, however, the call is a local one, the relay 322, energized as previously described, closes at contact 323 a shunt circuit round the contacts 253, 343 of the registers 203, 300, thus preventing the transmission to the local selectors of any impulses corresponding to the first two digits of the wanted line. The local selectors, which correspond to the third and final selectors, are, however, influenced during the return of the last three registers. As soon as the trunk finder, Fig. 4, left its normal position the contacts 423, 424 in the initial circuit of the register line relay 281 were opened, but its connexion to the calling line is maintained over contacts, such as 46, 47, 377<1>, 385<1>, of the different registers until all the registers have been restored, when the calling line is connected straight through to the trunk 372, 373. Release at end of conversation. The release of the group selector in known manner opens the test lead 405 or 408, thus de-energizing the test relav 425 or 426, which r