Patent GB-254790-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1925-04-06
Abstract: 254,790. Automatic Telephone Manufacturing Co., Ltd., (Automatic Electric Co.). April 6, 1925. Automatic exchange systems.-A call from one exchange to another may be set up over different routes, for example through different intermediate exchanges or over different levels leading to the same exchange, according to the idle or busy condition of the groups of trunks encountered. The change of route is effected generally by codechanging arrangements in a code-translating register-controller, although in some instances it may be effected without tho intervention of the register-controller. Two systems are described. In the first system, Figs. 1-6, the invention is illustrated in its application to the calls originating in a small outlying exchange of 2000 lines connected by a single group of 30 trunks to the nearest exchange of a neighbouring network, all outgoing calls being carried by this group of trunks. Local calls are made over the 4th and 5th levels of the first selectors, and the registercontrollers are arranged to release themselves immediately in response to the local exchange designation. The 30 outgoing trunks are connected in the 3rd, 6th and 9th levels of the first selectors and the register-controllers are divided into three groups, each group extending outgoing calls preferentially over a different level but being capable of extending them over the other two levels if all trunks in the preferred level are busy. For example, in the register-controller illustrated, the three outgoing levels ara given preference in the order 9, 6, 3. This is effected by connecting, at the translating frame IDF, Fig 3, the firstdigit terminals of all exchanges except the originating exchange to a circuit 404 which is normally connected to the 9-impulse wire of the sending switch. If however all trunks in the 9th level are busy, a chain circuit energizes relay 111, Fig. 2, which connects ground through a resistance 122 to circuit 112 for the purpose of partly energizing a two-step relay 401, which attracts its armature 403 to transfer the circuit 404 to the 6-impulse wire. If all trunks in the 6th level also are busy, a chain circuit energizes relay 110, Fig. 2, which short-circuits resistance 122 so as to energize fully the relay 401, which attracts its armature 402 to transfer the circuit 404 to the 3-impulse wire. The busy relays 109, 110, 111 also control codechanging circuits 113, 114 leading to registercontrollers of the other two groups, in which the order of preference is different. In the second system, of which the lay-out is shown in Fig. 14, calls from exchange A to exchange D are normally made via exchange C over the 3rd level of selector (S) and the 6th level of selector (S<2>), but if all trunks in its 3rd level are busy, selector (S) rises automatically to its 4th level and extends the call via selector (S') in exchange B. The trunks to exchange D occupy the same level in selector (S<1>) as in selector (S<2>) so that no change of code is necessary in the register-controller. Calls from exchange A to exchange C are normally made over the 3rd level of selector (S) and the 5th level of selector (S<2>), but if all trunks in the 3rd level are busy, selector (S) rises to its 4th level and either causes the release of the outgoing connection and the transmission of a busy signal from the register-controller, or else (if a slight alteration has been made in the circuit of the registercontroller) causes a change of code from 3, 5 to 3. 4, 5 so that the call is set up via selectors (S<1>), (S<3>). Similarly calls from exchange A to exchange E are normally madp via selectors (S), (S<2>), (S<6>) (code 3, 2) but may alternatively be made via selectors (S), (S'), (S<3>), (S<6>) (code 3, 4, 2). The change of code in these cases is effected by a relay 402<1>, Fig. 11, which is energized by the rise of the first selector to its 4th level if the exchange register OR<1> has been set to the designation of exchange C or E. The relay 402<1> causes the insertion of a second digit 4 which is normally skipped. First system. Registration of call by exchange register OR, Fig. 3, and number registers DRI - - DR4, Fig. 6. The energization of relay 9, Fig. 1. causes the switch DS to operate in the usual way to find an idle register-controller, whereupon relay 4 becomes energized, closing a circuit 54 for relay 301 and a loop circuit 52, 53 for line relay 22 of selector FS. Relay 301 connects circuit 112 to relay 401 to effect a change of code if necessary. The first dialled digit is repeated over circuit 12, 55, 201, 210 to the vertical magnet 417 of the Strowger exchange register OR. A series relay 201 energizes relay 202 so that at the termination of the digit the relapse of relay 201 momentarily energizes magnet 205 to step the switch S to its second position. The second digit is therefore repeated to the rotary magnet 416 and the switch S moves to its third position, and subsequent digits are recorded on the registers DR1 - - DR4. Transmission of impulses by the sender, Fig. 4. In the third position of the switch S, as soon as the two exchange digits have been recorded. a circuit 216 is grounded to close an interrupter circuit for magnet 315 which steps the switch SS. At the first step, a relay 302 is energized and opens a short-circuit across impulse contacts 314. Relay 302 also energizes magnet 211 and locks relay 301 to prevent the register-controller from being released while a digit is being transmitted. Impulses are now sent at contacts 314 to relay 22 until wiper 317 reaches the conductor jumpered at the IDF to the terminal on which has been set the exchange register wiper 412 which at this time is grounded through wiper 214, whereupon the relay 303 is energized, which locks itself, short-circuits the impulse contacts at 310, deenergizes magnet 211 to advance the switch S' to its second position and closes a selfinterrupting circuit for magnet 315 to drive the switch SS to normal. Then after a moment relay 302 relapses and unlocks relay 303. The next digit is transmitted in the same manner under control of the second wiper 413 of the exchange register, and so on. If there are only three digits in the code number of the wanted exchange, the terminal engaged by the fourth wiper 415 of the exchange register is jumpered to a skip wire 218 to step the switch S<1> instantly through its fourth position. The digits corresponding to the settings of the register DR1 - - DR4 are then transmitted, and the switch S<1> on reaching its ninth position grounds the wire 55<1>. Release of register-controller. The grounding of wire 55<1> energizes the switching relay 10, Fig. 1, which locks itself and de-onergizes relays 8. 9, the connection now being held from contact 105, Fig. 2, in the outgoing repeater R. Relay 4 is de-energized and releases the registercontroller, and the relapse of relay 301 closes circuits for restoring the registers and associated switches. Local call. The exchange digits for a local call set the register OR to a position in which it operates a shaft contact to ground the circuit 55<1>, so that the switching relay 10 is energized immediately and the register-controller released, the subsequent number-digits proceeding direct to the selectors. Second system. It will be seen from Fig. 11 that if the exchange register OR' is set to exchange C a relay 401' is energized over the first wiper 421<1>. Relay 401<1> locks itself and connects terminal 429<1> to the 3-impulse wire so that the first outgoing digit will be 3. The third digit is 5. The second and fourth digits are omitted, the terminals 430<1>, 432<1> being connected to the skip wire 417<1>, in the one case over a back contact 402<1> and in the other case direct. If the first selector FS', Fig. 7. has no idle trunk in its third level it rises automatically to its fourth level and operates a shaft-contact to close a circuit 21', 37<1>, 418<1>, Fig. 11, to energize a relay which locks itself and opens the loop circuit 38<1>, 39<1> so as to release the selector. The same relay disables the sender and connects busy tone to circuit 41<1> to notify the subscriber that he should hang up. If however the connection between terminals 451<1>, 453<1> is cut and a connection made between 453<1>, 452<1>, the effect of the selector FS<1> rising to its fourth level is to energize relay 402<1>, which inserts the missing second digit (4). The operations are the same if the register OR' is set to exchange E, but in this case the third digit (2) is controlled by the energization of a meter M, which records how many calls are made to the exchange E. Group selector FS', Fig. 7, which on being set to its third level rises automatically to its fourth level if there are no idle trunks in the third level. While impulses are arriving, two series relays 93<1>, 94<1> are energized in the circuit of the vertical magnet 75<1>. Relay 94<1> energizes the stepping relay 96<1> which locks itself up. If all trunks in the third level are busy, a circuit 69<1> is grounded through chain contacts in the outgoing repeaters and energizes relay 95<1> over an auxiliary vertical wiper 68<1>, so that upon the relapse of relays 93<1>, 94<1> the vertical magnet 75<1> is energized instead of rotary magnet 77'. Magnet 75<1> unlocks relay 96<1> which de-energizes magnet 75<1>, and relay 96<1> is then again energized by relay 94' which has again been energized in series with magnet 75<1>. Relay 95<1> is now deenergized, the fourth-level terminal of wiper 68<1> being dead, so that the relapse of relay 94<1> is followed by rotary hunting in the usual manner.