Patent GB-136207-A (GB)
Title: Improvements in Automatic Telephone Systems.
Inventor: CROSS WILLIAM
IPC: B21G1/00
Filed: 1918-10-11
Abstract: 136,207. Cross, W., (Hulfish, D. S.). Oct. 11, 1918. Automatic exchange systems and apparatus.- In order that a subscriber calling at an idle hour, such as at night, and failing to obtain a desired connexion because of a defective switch, may use a different switch when repeating the call, the restoration of the switch first used is delayed until a second similar switch has been taken into use. Special means are also described for effecting the necessary change-over between successive sets of selecting-impulses. The operation of the system for a normal call will be described first, and then the restoration arrangements for slack hours. The invention is described as applied to a system in which a calling line, Fig. 8, is connected to a desired line over line and group finders 101, 102, Fig. 4, (together forming the ,equivalent of a twoco-ordinate call-finder), a pilot or controlling switch 103, Fig. 5 and a " register '' or tens selector 104, Fig. 6. These switches 101 - - 104 are permanently associated and form part of a connecting " division '' or " set." Each switch is set by means of the escapement magnets 121 - - 124, the whole of the controlling-relays being shown in Fig. 9. Construction of switches. This is the same as that described in Specification 121,471, in which after use, the brushes are advanced electro-magnetically to a sub-normal position and are then restored to normal mechanically by a powerdriven oscillating member. Connexion of calling-line, Fig. 8, to called line. Figs. 4 to 6 and 8, 9 of the drawings form one complete Figure. with Fig. 6 to the right of Figs. 4 and 5. In these Figures, each switch terminal is represented by a circle and each brush by a small rectangle connected by a lead to its feed terminal. Brushes shown between terminals, as in Fig. 6, will engage the terminal at the half step. A terminal is identified hereinafter by giving first the number of the switch, then the level number, and then the terminal number in the level; thus 103-2-6 means the sixth terminal in the second level of switch 103. Similarly, a brush is identified by the location of its feed terminal; thus brush 103-2-25 means the brush, the feed terminal of which is the 25th terminal in the second level of switch 103. Switch 101 has some of its levels omitted from the diagram. Operation of call-finder, comprising group-finder 102 and line-finder 101. When a subscriber 156, Fig. 8, removes his receiver, his line relay 149 puts selectable potential upon his terminal in the line-finder 101, and also upon the group wire 305 connected, say, to terminal 102-1-14. The pilot switch 103 being in its normal position, with its brushes engaging the first and thirteenth vertical rows of terminals as shown in Fig. 5, a circuit is closed through the escapement magnet 122 of the group-finder 102, brush 102-4-25, wire 324, contacts of pilot switch, back contacts of test relay 138, wire 306, and armature of group calling relay 146 to ground. This circuit is interrupted at brush 102-4-25 as the brushes of the group-finder come into their half-step position, being completed again when the full step position is reached. The step-by-step movement of the group-finder brushes thus continues until the test brush 102- 1-25 reaches the terminal 14, say, of the group containing the calling line, whereupon the test relay 138 is energized to open the circuit of the escapement magnet 122 and to close the circuit of magnet 123 so as to move the pilot switch into its second position, wherein its brushes engage rows 2 and 14. The escapement magnet 121 of the line-finder 101 is then energized to move its brushes step by step over the line terminals, until its test brush 101-20-0 reaches the test terminal 101-20-4, say, of the calling line, whereupon the test relay 138 is again energized to open the circuit of magnet 121 and to move the pilot switch into its third position, wherein its brushes engage rows 3 and 15. A circuit is then closed from battery over resistance 134, Fig. 5, group and line finders as adjusted, to the cut-off relay 148 of the calling line. (The several sets of terminals in the group-finder 102 are connected to corresponding sets of brushes (not shown) in the linefinder 101 in a manner similar to the connexion of terminals 102-1-2, 102-2-2, 102-3-2, and 102-4-2 to the brushes 101-17-0, 101-18-0, 101-19-0, and 101-20-0.) Adjustment of " tens register 104, Fig. 6. A loop circuit is now closed through the calling line, this circuit including the relays 141, 142, Fig. 9, brushes 103-5-0 and 103-4-0 of the pilot switch. wires 311, 312, brushes of switches 101, 102 as adjusted, and the calling line. The operation of the impulse-sender opens the line circuit a determined number of times by the disengagement of springs 151, 152. These impulses are repeated by the relay 141 to the escapement magnet 124 of the tens register 104, the brushes 104-1-0, 104-2-0, 104-3-0 of which are adjusted as desired. At each de-energization of relay 141, an impulse is sent also through the upper winding of a relay 139, Fig. 9, and at each half step of the brushes of switch 104 an impulse is sent by brush 104-6-0 through the lower winding of relay 139. As the brushes of switch 104 complete their step, a further impulse passes through the lower winding of relay 139 to charge a condenser 135, Fig. 6. The relay 139 is thus maintained energized as long as selecting-impulses are received, but when these cease, relay 139 de-energizes and closes the circuit of relay 138 to move the pilot switch into its fourth position, wherein its brushes engage rows 4 and 16. Ringing-current. Connexion having been made with the required line over a connector (not shown), the pilot switch moves into its sixth position, in which the ringing generator 145, Fig. 9, is connected to the selected line over interrupter 154 and relay 153, which is energized to disconnect the ringing-relay 144 when the subscriber replies. Talking-circuit. The called subscriber is supplied with microphone current over relays 14U. 143, this circuit being connected to the similar circuit of the calling-subscriber by means of condensers 131, 132. Normal restoration of switches. In order to prevent interference with other lines during restoration, the switches are not restored simultaneously. Each switch is advanced electrically to its ultimate or sub-normal position and is then mechanically returned to its normal position. When the calling-subscriber replaces his receiver after a conversation, the relay 141 de-energizes. releasing the slow-release relay 160, which advances the pilot switch into its tenth position, wherein the brushes engage the tenth and twentysecond rows of terminals, and all connexions to the calling and called lines are opened. The pilotswitch then closes circuits for the escapement magnets of the switches 101, 102, 104, whereby the brushes of the line-finder 101 are advanced to positions 12 and 24, whereas the brushes of switches 102, 104 are advanced in positions 11 and 23 in each switch. When the brushes of switches 102, 104 have reached terminals 23, a circuit is closed for relay 138, which moves the pilot switch into its eleventh position, wherein its brushes engage the eleventh and twenty-third rows of terminals. The brushes of the line-finder 101 and the pilot switch 103 are now restored mechically by the engagement of the clutch arm with an oscillating lug. The pilot brushes come to rest in a pre-normal position O, in which further circuits are closed to advance the brushes of switches 102, 104 one step, so that these are returned to normal on the next swing of the lug. When they reach their normal positions a circuit is closed to move the pilot brushes to their normal position Special restoration arrangements adapted to ensure that a subscriber, calling at an idle hour such as night and failing to obtain full service because of a defective switch, shall receive service from a different switch when repeating the call. For this purpose, the restoration of the switch first used is delayed until a second similar switch has been taken into use. Fig. 10 shows parts of two sets of switches arranged in this way. On the left of this Figure are shown four levels of the pilot switch 103, Fig. 5, the third level of the " tens " register 104, Fig. 6, and the second level of the group-finder 102, Fig. 4, while on the right are shown the similar levels of the corresponding switches 1032, 1042, and 1022 of a second set or " connecting-division." As previously described, when the switches 102, 104 reach their normal position, a circuit is closed to move the pilot brushes to normal, this circuit being shown in Fig. 10 as including the relay 138 (controlling the pilot clutch magnet), contact 103-2-12, wire 335, contact 104-3-12, wire 314, contact 102-2-12, wire 394, to earth over key 161. If the key 161 is closed, the restoration of switch 103, and consequently the making operative of the whole connecting-division 102, 103, 104, 106. is independent of any other " connecting-division. " If, however, the key 161 is open, wire 394 is only earthed over wire 3292 and brush 1032-9-25 of the pilot switch 1032 of some other " connecting- division " when its pilot reaches its third position, in which the earthed brush 1032-9-25 engages the, contact 1032-9-15. Consequently, if the key 161 is opened at night, and a subscriber, failing to obtain a connexion because one of the switches 102, 103, 104 is defective, replaces his receiver, these switches will not be restored, and on a subsequent call the subscriber will be connected to a different set of switches, the common group call relay 146 extending the call over wire 306, contacts 103-4-15 to 103-4-23, and wire 397, to the next " connecting-division."