Patent GB-686533-A (GB)
Title: Improvements in or relating to automatic telecommunication exchange systems
Inventor: HARTLEY GEORGE CLIFFORD
IPC: H04Q3/58
Filed: 1949-04-20
Abstract: 686,533. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. April 20, 1949, No. 10459/49. Class 40 (iv). In a rural automatic exchange (R.A.X.) in which out-going calls are set up by an operator at the main exchange, if all junctions are busy the calling subscriber may dial his own number which is then stored for future use in recalling him. In one system described below, the number is sent over an order wire circuit superimposed on a junction to an indicator at the main exchange. In another system the number is stored at the R.A.X. and sent to the main exchange under the control of an operator when a junction becomes idle. In both systems the R.A.X. comprises relays only. As shown, with the drawings arranged according to Fig. 11A, a calling line is extended by relay 1KA or 1KB to one of the links A, B and thence by relay 2OHA or 2OHB to an idle connecting circuit in which line relay 3A energizes. Dial tone is applied through a third winding of 3A, and this relay responds to dialled impulses. Assuming that O is dialled, relays 3MA, 3MD, and 3TT (not shown) operate and 3H is connected to lead JT and, if there is an idle junction, operates in series with junction relay 5JT before slowoperating relay 3G pulls up. Relay 2IHJ energizes in series with 5K and connects the junction to the connecting circuit, in which 3OG transfers the calling line from 3A to line relay 5A of the junction. The call is then established by the operator at the main exchange. If there is no idle junction, 3H is inoperative and the subscriber hears busy tone. He may now dial an extra digit, e.g. 1, which results in the operation of 3GA (not shown). Relay 3H now operates over lead BT in series with 6JBT in a " booking " circuit, and the calling line is connected thereto by 7JBH which energizes in series with 6K and locks in series with 3OG. Line relay 6A and guard relay 6B operate, establishing a composite calling circuit over the junction. Impulses are sent over this circuit by self-interrupting relay 6PV until it is cut off by 6DZ which is controlled by 6TA, 6TB so as to operate after one impulse if 6CB is back and after two impulses if 6CB is up. The meter 1M of a coin box line is connected to battery and 6CB energizes when such a line calls. At the main exchange 9L, 9B energize, the impulses are repeated to 9X, 9Y, and 9TA, 9TB, 9SA are operated, with the result that lamp AL lights if two impulses are received. Relay 6DZ also connects up 6ST which applies dial tone. The booking circuit is now ready to receive the digits of the calling party's own number and repeat them over the composite circuit. Relay 6C is operative during each digit and controls 6TA, 6TB, 6TC in order to effect release of the composite circuit and of the connection to the booking circuit when the number is complete. The digits are repeated at the main exchange to indicators A1, A2 of the kind described in Specification 538,723. and relays 9SB, 9SC operate in turn under the control of 9TB, 9TC, 9TD. When 9L is released, the display remains until the reset key is pressed when 9SA, 9SB, 9SC are released. Further calls may be booked on indicators B1, B2; C1, C2, &c. When all the indicators are full, 9SM sends a signal back to operate 6LB in the booking circuit to open the lead BT. Relay 9RS controlled by the reset key sends a signal to release 6LB. If the subscriber does not complete dialling, any display is cancelled.