Patent GB-141550-A (GB)
Abstract: 141,550. Western Electric Co., and Deakin, G. June 6, 1919. Automatic exchange systems.-Initial zeros in a subscriber's number are replaced by a prefix signifying the number of zeros omitted. The number transmitted by a calling-subscriber is recorded on registers at the exchange, and the prefix causes the re-insertion of the missing zeros in the register record. The invention is of special utility during the piecemeal conversion of a large district from manual to automatic, to enable all the subscribers to be listed in the directory on a common plan. For example, in a system of 700,000 subscribers (70 exchanges of 10,000 each) the figures 8, 9, and 0 do not ocur in the first digit, and may be used to signify one, two, and three missing zeros in the thousands, hundreds, and tens digits. The subscribers' impulse dials are marked:- 1. 2. 3. 4. 5. 6. 7. 8. 9. 0. A. B. C. D. E. F. G. H. K. L. and a subscriber's directory number ordinarily consists of two letters, indicating the exchange, followed by a four-digit number. Thus GERRARD 4444 might be BL 4444; but GERRARD 444 would be HBL 444 (not BL 0444), GERRARD 44 would be KBL 44, and GERRARD 4 would be LBL 4. The register circuits are shown in the figure. The, exchange digits, such as BL, are recorded on the registers 30, 33, and the four-figure number on registers 35, 38, 40, 43, the registers being set in known manner, in the 2nd, 6th, 8th, 10th, 12th, and 14th positions of the sequence switch 24, by relays 22, 23 controlled by the subscriber's impulses. In the case, however, of calls marked with the special prefix H, K, or L, the operation is as follows : The impulses representing this prefix set the register 30 in position 8, 9, or 0, closing circuits for setting an auxiliary switch 32 in position 4, 3, or 2, and the register 30, if it is in position 8 or 9, is then restored to zero. The connexions of the registers have been altered by the switch 32 in such a way that the exchange digits, such as BL, are now recorded on the registers 30, 33 in the 6th and 8th positions of the switch 24, and the other registers are set in subsequent positions, but those registers which correspond to initial zeros in the called subscriber's number are passed over and left in zero position. For example, suppose the wanted number is KBL44 (=BL0044). When the calling- subscriber 20 is connected to a register-set, the switch 24 moves to its 2nd position, closing at 28 a tone circuit for indicating that impulses should ba transmitted. The impulses representing the prefix K set the register 30 to position 9, and at their termination the switch 24 advances to its 6th position. As the switch 24 runs through its 3rd and 4th positions, a circuit 58 top, 64, 65 is closed to drive the switch 32 to its 3rd position. When the switch 24 reaches its 5th position, the register 30 is restored to zero over a circuit 58 bottom, 61. In the 6th position of the switch 24, the impulses corresponding to the digit B set the register 30 over the circuit 29 bottom, 34 top, and in the 8th position of the switch 24, the digit L sets the register 33 over the circuit 37 top, 36 top. The registers 35, 38 are now passed over, there being no circuit for them in the 3rd position of the switch 32. In the 10th position of the switch 24, the tens digit sets the register 40 over a circuit 37 bottom, 66, and in the 12th position of the switch 24, the units digit sets the register 43 over a circuit 42 top, 41 bottom. The switch 24 is then run through its 14th position by a circuit 67 bottom, 68, and in passing its 15th position closes a circuit 45, 46 for starting the sequence switch 47, which governs the successive operations by which the registers control the establishment of the wanted connexion.