Patent GB-205802-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1923-10-15
Abstract: 205,802. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Ostline, J. E.). Oct. 18, 1922, [Convention date.]. Order apparatus.-In a telephone system in which the number of a wanted subscriber in a manual exchange is set up on a call-indicator at the manual operator's position, the digits of the wanted number are transmitted over an inter-exchange trunk from a distant automatic exchange, by means. of a code comprising combinations of impulses differing in number and order and also in strength or polarity, there being in no case more than three impulses for each digit. The codes used for each of the station and numerical digits are shown in Figs. 7 and 9. The code digits are decoded at the call-indicator to control number lamps arranged on the decimal principle, by means of the relay switching arrangements shown in Fig. 6. The code impulses are transmitted over the two trunk conductors in series to relays 325, 326, 327 which respond respectively to all negative impulses, weak positive impulses, and strong negative impulses. Each set of ten. indicator lamps shown at the bottom of Fig. 6 is controlled by four " set-up " relays, 401-404 &c., energized singly or in combination. From a consideration of Figs. 7 and 9 it will be seen that each digit contains two negative impulses which mav or may not have a positive impulse preceding or following the first negative impulse. A positive impulse preceding the first negative impulse of a digit, operates a " first set-up " relay such as 401 over the circuit 329, 338, 354, the relay remaining locked up over the common grounded lead 311. The first negative impulse of a digit completes circuit 328, 333, 332, 331 in which marginal relay 331 does not energize but relay 332 energizes, prepares a locking circuit which is as yet short-circuited, and energizes relay 340 over contacts 337, 349. Relay 340 switches over the lead from relay 401 to relay 411 in the next lamp group, and prepares a locking circuit over relay 339 and contact 352 which is as yet shortcircuited. If this first negative impulse is a strong one, a " second set-up " relay 402 is operated over contacts 330, 335, 351. At the end of the impulse when relay 325 falls back, relay 331 energizes over both its windings in series with relay 332 and operates contact 335. A positive impulse coming in after the first negative impulse will operate a " third set-up " relay over the circuit 329, 338, 359. The second negative impulse, if strong, causes the operation of a " fourth set-up " relay 404 over contacts 330, 335, 350. The energization of relay 325 due to' the second (weak or strong) negative impulse short-circuits relay 332 over contacts 328, 333 and the succeeding opening of contact 328 causes relay 331 also to fall back and permit relay 339 to operate in the locking circuit of relay 340 and transfer the leads controlled by armatures 349 -- 351 from the station relays STA to the thousands relays TH. Thus it will be seen that the code impulses transmitted from the distant exchange are decoded by the relays 325-327 and thereby caused to control the station and numerical " set-up " relays in accordance with the tables shown in Figs. 7-10. At the end of the impulses, relay 347 grounds conductor 380 and the selected lamps are lit to display the wanted number.