Patent GB-451512-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1935-02-06
Abstract: 451,512. Automatic exchange systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, TAYLOR, R., 30, Oulton Road, Wavertree, and BAKER, G. T., 31, Wharnecliffe Road East, all in Liverpool. Feb. 6. 1935, No. 3903. [Class 40 (iv)] In the event of a bidirectional final selector encountering a busy condition on the line or group of consecutive lines on which it is numerically set, common apparatus is taken into use to search over additional or overflow lines leading to the same subscriber and to reset the selector on an idle one of such lines which may be located anywhere in its banks or to a position from which a busy signal is sent. When a final selector encounters a busy condition of an individual line or of a P.B.X. group, the operation of relay G connects battery to one of the start wires OLS, ELS and marks the final selector in the vertical banks AWF of the finders F. Two sets of auxiliary apparatus are provided for 8 groups of 100-point final selectors or 4 groups of 200-point final selectors as shown, and each set acts as a reserve for the other. Relay SA energizes and connects up start relay ST, SB being inoperative unless battery is applied to the start wire by two relays G simultaneously, in which case it pulls up and takes into use the other set of apparatus also. The finder F steps vertically until LK operates over the vertical bank AWF and then rotarily until RS operates over wiper F8. Relay HR energizes over wiper F2 and switching relay H (inoperative) holding ST and opening the start wire. The marker M now steps vertically to the same level as the final selector, the vertical bank AWM of the marker being multipled with the vertical banks AWP of the selectors it serves and the relevant terminals being connected over wiper F7 to relay VT which operates followed by VTR. Since the two markers may be hunting at the same time, the two relays VT are arranged to operate to battery and earth respectively. Circuits are closed by VTR for the rotary magnets RM, 1RM of the marker and final selector under the control of stepping relay GA until the selector reaches its 11th position when GA is held in series with EC over wiper F4, and the marker then stands in a position corresponding to the busy line or group. Relays EL, CO are connected to wiper F1 of which the terminals corresponding to final selectors serving the same group of 100 lines are connected in multiple to a particular wiper of the marker M. In the case of 200-point selectors, the multiple connections may be changed over by relay WS which is dependent on the wiper-switching relay of the selector. Terminals of the marker for which no overflow lines are provided are connected to earth, and relay CO energizes and short-circuits HR to operate switching relay H of the selector, whereupon a busy signal is sent in the usual manner. The relapse of HR restores the auxiliary apparatus. If overflow lines are provided, relay EL energizes in series with CO (inoperative), completing circuits for stepping the switch ALH to a position marked by the marker M and connecting up the rotary magnet IRM to restore the selector to normal. Relay IG energizes when the switch ALH reaches the marked position and connects IH to wiper ALH3 to test the first overflow line. If this is busy, the switch ALH resumes stepping until an idle overflow line is reached, when IH pulls up and holds IG. The bank S3 of the sending switch S is now marked over wipers ALH5, 6 to control the resetting of the final selector on the idle overflow line. Relay IH completes circuits by which the sending switch magnet interacts with the vertical magnet IVM of the selector until SS picks up the first marking, whereupon SZ operates and transfers the driving circuit to the rotary magnet IRM. The second marking is picked up by CO which brings about the operation of switching relay H and the restoration of the auxiliary apparatus. If the switch ALH finds no idle overflow line, BC energizes at the beginning of the second revolution, connects up IH and applies markings by which the final selector is reset to the 11th position of the first level in order to send a busy signal. The 11th positions may be used to accommodate overflow lines, and when such a line is seized the busy signal is suppressed on account of the non-operation of G. Delayed alarm equipment is provided to operate if the auxiliary apparatus is held for an excessive time.