Patent GB-668261-A (GB)
Title: Automatic switching system applicable to telephony
IPC: H04Q3/42
Filed: 1945-11-05
Abstract: 668,261. Automatic exchange systems. COMPAGNIE GENERALE D'ELECTRICITE. Nov. 5, 1946 [March 26, 1943], No. 29292/45. Class 40 (iv). In an automatic exchange system all selectors at any given stage are marked over a common marking multiple which is also common to the appropriate digit switches of all the register controllers, each register controller applying the marking potential from an insulated batting source individual to itself. This source is also used for energizing other similarly commoned wires, e.g. for controlling PBX hunting, repeated hunting over a busy group, or for controlling the extension of false calls to an operator's position. Allotment of Register Controller. Relay A operates to the subscribers loop and operates start relay M1. Relay MC2 which is common to all call finders RC2 of the same group operates followed by MC1, which is common to all the secondary finders RC1. MC1 operates relay 7D in the allotter (Fig. 3). Relay M1 also operates differential relay 4D of the allotter which locks in series with 3D (which however does not itself operate until slow relay T is operated by M1) and removes the shorting earth on wire 3. A subsequent call in the group operates 5D and 6D in the allotter in the same manner. MC2 earths the contacts M of all the connecting circuits in the bank of the finder switch E of the register (Fig. 4). Meanwhile, relay 3D starts switch RT hunting for a free register and when one is found relay 8D in the allotter operates in series with relay 7 in the register and cuts the circuit for RT and releases 4D or 6D by energizing an opposing winding. Relay 8D falls, short circuited by contact 72 of the register relay 7 and relays 3D or 5D follow. If relay 3D or 5D does not operate within a certain time relay 1D is operated by cam 8, and locks, and after a further interval 2D operates over cam 9 which energizes 4D and subsequently 3D when 2D releases. Switch RT then hunts for a register as before. In a disengaged register relay 7 remains operated over 72 during the whole of the time that MC1 is operated, i.e. as long as any subscriber is calling, without the aid of the allotter. Register hunts for link circuit. Relay 7 operates 13 and finder switch E hunts until stopped by relay 14 operating over the M wire. Relay 14 connects the upper winding of differential relay 13, to the M wire and if no other relay is connected thereto the current in the upper winding releases 13 which shunts out 14. Two relays 14 of different registers cannot operate over the same M wire when they are shunted by a coil of 13. Relay 16 operates, whereupon relay 8 energizes over its lower winding and locks over its upper winding to wire M. Relay 14 and the upper winding of 13 are shunted out so that the latter re-operates and releases 16 which by opening the energizing circuit of 8 allows the operation of the differential relay 9 which has its windings in series with those of 8. Secondary finder operates. Secondary finder RC1 then hunts for a disengaged primary finder, until stopped by 14 operating over the T-wire. Relay 13 tests for double connection, as above, and de-energizes if the finder is free, whereupon 16 operates, followed by 10. Relays 10 and 11 behave similarly to 8 and 9 and lock up their upper windings. Relay 6 operates in series with 02 in the primary finder which latter does not operate however. Primary finder operates. Relay 6 energizes the primary line finder magnet RC2 over the B-wire and stopping and double testing take place as before. Relay 16 operates, whereupon impulse relay pulls up over its lower winding, followed by 3 which locks and operates 5. Switching relay C2 in the primary finder operates and locks to battery connected to T1 by relay 5 which also busies the link circuit by battery on M. In the subscribers circuit F operates in series with A. Relay 1 is now held over the subscribers loop and relay 5 causes X4 to advance a step and dial tone is sent out from source 22. Relay 7 releases followed by 8, 9, 10, 11, the last opening the circuit of the lower winding of 1. Operation when single finder only is used. If a first choice link circuit is free (Fig. 6) its relay 3 is released and its M-wire is not connected to battery from a register controller. Relay M2 can therefore operate cutting off the start circuits of the second choice finders. The finder hunts under control of the register in which relays 8, 9, 10 and 11 operate as before, but 6 does not as no earth is encountered on the C-wire. In this case the initial circuit for the lower winding of relay 1 is made over the unoperated contact 61. Setting the digit switches. The first dialled digit is repeated by 1 to set the reverse drive digit switch X1. At each impulse the magnet armature removes a short circuit from 2 which operates, opens the magnet circuit and reoperates 1 if and when the subscribers loop is re-closed. Dialling relay 4 steps switch X4 to positions 2 and then 3 to enable the reception of the hundreds and tens digits on X2 and X3. X4 is then driven to the half-way position whereupon it behaves as a digit switch and registers the units digit. Waiting tone from source 21 is then transmitted to the subscriber. Setting the group selectors. As soon as the first digit is received and X4 is at position 2 sequence switch X5 goes to position 1 and the thousands selector rotates to the initial contact set of the desired thousands group, whose C-wire is marked from battery from the individual source 23, 24 by bank a of digit switch X4 and when this is reached 15 operates, followed by 13. Selector switch RS1 then hunts for a free outlet in the group and when this is found 14 operates over the T-wire and interrupts the drive. Low resistance upper winding of relay 13 shunts 14 and busies the outlet, and 13 releases due to the differential action, thereby operating 16 provided the second digit has been registered so that the short circuit over bank e of X4 in position 2 is removed. Relay 16 energizes X5 and relay 12 which then locks and places battery on the outgoing T- wire to busy the hundreds selector. Relay 15 releases followed by 14 and 16 and X5 goes to position 2. The hundreds selector RS2 then hunts for a free outlet of the group registered on X2 under control of relays 15, 13 and 14 as in the first group selector. If two switches controlled by different registers attempt to seize the same outlet, both relays 14 operate, but on being shunted by the relays 13 at least one will release and restart the corresponding selector. All outlets of a group busy. It all outlets are busy the selector continues to step round again and in doing so passes a " busy " position in which the C-wire is connected to wire 17 and the momentary operation of 22 connects up 21, 20. If on the second time round a free outlet is found 14 operates and seizure takes place in the normal manner. If no free outlet is found 22 again operates at the busy position and this time locks over contact 211 and short circuits relay 3 which falls and releases the connection, and the calling subscriber whose A- relay releases receivers busy tone over relay F which locks to the calling subscriber's line. Setting the final selector. Relay 16 operates provided the tens digit has been received, shunts the high-resistance winding of 15, thereby allowing S2 to switch through in the hundreds selector and energizes X5. Relay 15 releases followed by 14, 13 and 16 and X5 goes to position 3. S2 locks to the T-wire. The final selector hunts under control of 15 for marking applied by X3 to the C-wire. If the units digit has been received wiper j of X4 will be off normal and X5 goes to position 4 and 15 falls. The final selector then hunts under control of 15 for the units position whose C-wire is marked by X4. Called subscriber busy. Relay 14 does not operate but busy relay 17 does and X5 passes to position 5 and thence to 6 whereupon 3 is short circuited and falls disconnecting 5, whereupon the connection is released and busy tone is sent over relay F of the calling subscribers circuit as described above. Called subscriber free. Relay 14 operates in series with A and F in the subscribers line circuit and connects in the upper low resistance winding of 13 to busy the line and release 13. Relay 16 operates, energizing X5. The high resistance coil of 15 is thus short circuited, enabling C0 in the connector to switch through. Relays 15, 14 and 16 release, the last driving X5 to position 5 and thence to position 6. Relay 5L in the link circuit (Fig. 2) operates, followed by 1L, 4L, 3L of the link circuit which transfer the calling loop to feed relay 1L of the link. Relay 3L closes a locking circuit for 5L. Ringing and metering. Ringing current is sent out from a source at contact 55L and when ring trip relay 6L operates to the called subscribers loop it short circuits the holding coil of 5L thus connecting up the called subscribers feed relay 2L which operates and reverses the direction of the battery to the calling subscriber. The subscribers meter C is operated over the C- wire over contacts 65L, 56L during the slow release of 5L. Relay 3L disconnects MC1 and busies the link against selection by a register. Release. For first party release points AB and EC are strapped. Release of either 2L or 1L then short circuits relay 4L which releases 3L and all the finder and selector circuit relays. The second party to release receives busy tone from relay F meanwhile. For calling party release points AB are strapped, and 4L is released as above when 1L releases. Release of 2L has no effect. For called party release points AD and CE are strapped. Release of 1L releases 4L as above. A and D are strapped to enable the calling subscriber to release if the called subscriber does not answer (3L and 5L up). For last party release points AC and D are all strapped together. 4L is short circuited only when 1L and 2L are released except when the called subscriber doe