Patent GB-624557-A (GB)
Title: Telecommunication system
IPC: H04M1/515
Filed: 1945-02-23
Abstract: 624,557. Automatic exchange systems and apparatus. STANDARD TELEPHONES & CABLES, Ltd. (International Standard Electric Corporation). Feb. 23, 1945, No. 4599. [A Specification was laid open to inspection under Sect. 91 of the Acts, Sept. 25, 1945.[Class 40(iv)] An impulse dial is pulled clockwise for the digits 1-5 and anticlockwise for the digits 6-0 and sends by means of a rotating rectifier a train of up to five impulses which alternate in polarity, the first impulse being positive or negative according as the digit is odd or even. A registercontroller for responding to such impulses is described, the system being of the kind disclosed in Specification 628,174. Specification 605,049 also is referred to. Construction of dial. In addition to the usual finger stop 35, an auxiliary stop 34 is provided between the finger holes 5 and 6. At its lower end the shaft 2 is connected through gearing 21 ... 24 to a shaft 29 carrying a rectifier 26 which has as its terminals a pair of wipers 27, 28 for engaging contact segments S1, S2 to be connected in the line circuit, the gearing being such that the rectifier makes one revolution while the finger plate moves through a distance of two finger holes. The return movement of the shaft 2 is effected by means of a spiral spring 41 which is attached at its ends to two enclosing discs 15 so that projections 16 on the discs are normally pressed against a stop 17. A pair of arms 14 fixed to the shaft 2 engage projections 18 on the two discs 15 so that according to the direction in which the finger plate 1 is pulled one or other of the discs is rotated away from the stop 17 to tension the spring 41. When the finger plate has been pulled to a point within two finger holes of the stop 35, the tip of the finger engages a lever 11 mounted on a sleeve 7 so that the remainder of the setting movement is imparted to a lever 8 which carries a pin P for controlling the spring assembly 40, the springs C1 being opened first and the springs C2 being closed just before the stop 35 is reached to connect the segments S1, S2 in the line circuit and send the first impulse. The polarity of this impulse depends on whether the digit is odd or even, and subsequent impulses which alternate in polarity are sent during the return of the finger plate. When the lever 8 is shifted from its normal position, a spring 9 attached thereto is lifted by the removal of a projection 36 from a recess in the frame to bring a second projection 37 into the path of the tip 38 of an arm 10 fixed to the finger plate, so that the sleeve 7 and pin P are restored during the latter part of the return movement, the impulse train being ended by the opening of the springs C2. Register-controller, Fig. 9. Relay RBR energizes when the calling line is picked up, and operates HR which holds over the line and connects up R1R. The opening of the line at springs C1, Fig. 7, when the dial is moved off-normal releases HR and thus prepares an A.C. circuit through polarized relays PR+, PR - which control parallel circuits through the windings of a differential relay DR -. The impulses received after springs C2 close energize PR+, PR - alternately, and DR operates and connects up R3R, R4R. If PR + energizes first, the impulses are recorded on a relay chain CR1 ... 5, whereas if PR - energizes first, they are recorded on a chain CR6 ... 0. At the end of the impulse train when springs C2 reopen, both PR+ and PR - are inoperative and DR falls back followed by R3R, R4R, the recorded digit being transferred to the relay register XR1 ... 4. Subsequent digits are received and registered in a similar manner. The selectors may be controlled by the method of potential comparison described in Specification 628,174, the relay registers being effective in turn to apply a potential marking to the out-control switch PO.