Patent GB-298165-A (GB)
Title: Improvements in telephone systems
IPC: H04M3/64
Filed: 1928-10-04
Abstract: 298,165. Standard Telephones & Cables, Ltd., (Assignees of Caverly, H. C.). Oct. 4, 1927, [Convention date]. Semi-automatic exchange systems.-Systems in which the wanted number is repeated verbally from a register-controller at an automatic exchange to the operator at a manual exchange by means of a "call-announcer" mechanism comprising photographic records of the sounds of the various digits are provided with the following features :-(1) The closure of a bridge across the inter-exchange junction at the automatic end causes the association of the manual operator's equipment with the incoming end and when the latter operation is completed the closure of a bridge at the manual end initiates the transmission of the wanted number. (2) The operation of a manual key at the operator's position to dissociate her equipment from the junction is only effective after the call announcer has sent the complete number. (3) The normal manual practice of pausing between the second and third digits and between the fourth and station digits of a wanted number is simulated and means are provided for altering the position of the pauses when a five-digit number is used. (4) Means are provided for preventing the transmission of a mutilated digit. Setting of registers and extension of call to manual exchange. The setting of the exchange registers and the operation of the district and office selectors 357, 1103, by translated routing- digits take place in known manner, and the four numerical digits and the station digit are repeated by relay 606 over relay 614 and wiper 802 to registers 1007 - - 1047. When the office selector is set a circuit to test the condition of the junction is closed from relay 201, Fig. 2, over brush 357, cams 358, 954, 717, relays 716, 704, cams 525, 356, brush 355, to relay 201. Relay 716 energizes, operating relays 720, 721, 737 and relay 737 drives sequence switch 700 to position 15 in which the circuit across cam 717 is open but is shunted by front contacts of relay 721. At the manual exchange relay 201 operates causing a switch 250 to hunt for the junction in use and when this is found, relays 207, 208, 203 operate connecting the left-hand winding of relay 209 across the junction. Relays 716, 720, 721 then release extending the junction circuit from cams 954, 525 over front contacts of 737, cams 900X, 900Y of the class register (in position 1 or 10 for a call-announcing connection) and the left-hand windings of repeating coil 292 to resistance 291 and relay 293. The reversal and increase of current in polarized and marginal relay 290 in the office selector 1103 causes this relay to aperate. Transmission of wanted number. Relay 209 energizes over the circuit just traced t connect the operators' headset to the junction, whilst relay 293 completes a circuit for relay 401 which however is short-circuited when relay 404 is operated so as to prevent the transmission of a mutilated digit. Relay 404 is operated over commutators 403, 402 at the times when the record drums of the call-announcer CA, which may be of the type described in Specification 298,164, are in operative position. When relay 401 operates, it completes a circuit from lead 406 over the right-band windings of repeating coil 292, leads 408, 409, to wiper 1006 so that the sound corresponding to the digit determined by the setting of wiper 1006 is repeated over coils 292, 204 to the manual operator. During the transmission relay 412 operates over leads 410, 405 and at the end of the digit relay 411 operates so that wiper 1016 is connected up for the next digit. When relay 413 operates at the end of the second digit, the primary circuit of coil 292 is open at a contact of relay 422 and no digit is transmitted during the third announcing period but a pause equal to the length of a digit is introduced. At the end of this period, relay 415 operates so that during the fourth announcing period wiper 1926 is connected up to transmit the tens digit. The operation of relay 418 unlocks relays 411 - - 414 and at the end of this digit relay 417 connects up units wiper 1036. For the sixth announcing period, relays 412, 411 reoperate and a second pause is introduced in a similar manner, after which wiper 1045 is connected up to transmit the station digit. Relay 413 then connects earth from lead 405 over contacts of relays 404, 401, 415, 417, 419, 411, 413, 417 and lead 423 to operate relay 524 which opens the junction circuit releasing relays 293, 290 and thereby effecting the release of the register-controller and the advance of the selectors to talking position. At the manual office, the operator if she has heard the number satisfactorily unlocks relay 209 by operating key 210 and completes the connection in the usual way. If desired she may converse with the calling subscriber before pressing key 210. Four-digit numbers having no station digit; time-alarm arrangements. If the position of the translating switch indicates that four digits only are required, the timing device which gives an alarm if all the digits are not registered within a certain time is reset over an arc of the units register. At the same time earth is connected to lead 424 and thence over lead 423 to relay 524. Five digit number (between 10,000 and 10,499). For such a call, a circuit is completed over the thousands and hundreds registers (in positions 1 and 0 respectively) to operate relay 958 which discriminates between two positions of the class register and operates relay 422 by means of which the circuits of the counting-relays 411 - - 420 are so modified that a pause occurs between the third and fourth digits.