Patent GB-529718-A (GB)
Title: Improvements in or relating to telecommunication exchange systems
IPC: H04M15/08
Filed: 1939-04-22
Abstract: 529,718. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., and PETERS, G. E. April 22, 1939, No. 12132. [Class 40 (iv)] The operations of identifying a line and signalling its number are speeded up by performing them simultaneously, the impulses which are used to step the identifying switches being fed also to the signalling equipment. The arrangements shown are designed to identify calling lines numbered 2000-6999 and 81300-81799, three bi-directional switches being used for identification. MF discriminates between four- and five-digit numbers over its vertical bank and identifies the 10,000's digit over its rotary bank, GF identifies the 1,000's and 100's digit over its vertical and rotary banks and gives access to the third switch LF which identifies the tens and units digits. GF is individual to MF as each 10,000's digit has a single corresponding 1,000's digit, but further MF switches could be used to accommodate a more extended numbering scheme. The subscribers' metering leads ML used for identification are connected individually to the rotary bank of LF, in groups of 10, 100 and 1,000 respectively to the vertical bank of LF and rotary and vertical banks of GF, isolating condensers IC, TC, HC being used between the successive connections. The vertical bank contacts of GF and the vertical and rotary bank contacts of MF are interconnected as shown, levels 2 to 5 being interconnected in a corresponding manner to level 6. The sequence of operations is controlled by switch SS. A number of storage circuits (above the upper dot-and-dash line) are provided in groups connected to the banks of switches FA to which access is given by switch AF connected to individual identification circuits. Detailed operation. When a call is completed, relay AS (not shown) in the storage circuit associated with the call pulls up and operates storage group relay GA which makes a circuit for start relays STA-STC of the individual identification circuits of which STA (say) pulls up and operates STR which provides a holding ground at points marked #. The start relays are marginal and more than one pulls up on simultaneous calls for identification. Sequence switch SS moves to position 2 in which the valve circuit at the bottom of the Figure is tested for response to the individual frequency A which each identification circuit uses. The frequency is applied over ssm4 and lead YL and if the response is satisfactory anode relay V causes SS to step to position 3, and also to position 4 if V relapses. Ground now applied over ssm4, 5 to magnet AFM causes the switch AF to hunt for the calling group of storage circuits marked over afm4, the hunt being stopped by T followed by TT whereupon SS moves to 5, T falls back and FAM hunts for the storage circuit marked by AS in bank fam2. When this is found, T re-operates followed by TU and SS moves to 6 in which FS pulls up, locks and steps SS to 7. Relay FS connects identification frequency A over afm6 to lead PL of the storage circuit and thence to the metering lead ML of the calling party. Relay SR. operates over ssm3 in position 7 and relay IR, connected to impulse springs IPS under the control of IG, impulses the vertical magnet MFVM until relay V in the valve circuit is operated by the frequency connected over lead ML to vertical bank mfvm2, whereupon SR is released and impulsing ceases. DR operates over mfv1 in the 1st digit is 8 (5 digit number), and LA operates over ssm2 and steps SS to 8. The relays LA ... LE operated by V over ssm2 are slow to operate to prevent interference by surges in the valve circuit. SS goes to position 9 when V releases, SR pulls up again and IR impulses the rotary magnet MFRM and, if DR is operated, also transmits ground impulses (10,000's digit) over afm5 and lead RL to the storage circuit, until relay V responds to the applied frequency. LB pulls up and, by connecting an acceptor circuit AC tuned to the identifying frequency to wiper mfrm1, effectively grounds at this frequency the condensers HC of the 1,000 group. SS moves to 10 and thence to 11 when V relapses, whereupon impulses (1,000's digit) are transmitted to vertical magnet GFVM and to the storage circuit. If DR has not been operated LB completes the impulse circuit for the 1,000's digit. The remaining digits are identified and transmitted to the storage circuit, the acceptor circuit being connected up in turn to the condensers of the 100's and 10's groups by LD and LE. The sequence switch is now in position 18 in which ground over ssm6, 7 and off-normal springs LON of LF operate the rotary magnet to release LF whereupon RA pulls up and completes the release circuit for GF. When this switch has released, RA falls back and RR pulls up to release FS which disconnects the identifying frequency and makes a release circuit for MFRM. When this switch has released, SS steps to 19 in which STR is shunted down and SS steps home. Calls to operators. The transmitted pulses must be A.C. instead of ground in order that they may be passed through the cord circuit. Contacts of fam 1 corresponding to operators' circuits are grounded, so that OD pulls up and connects up an A.C. source for impulsing over RL.