Patent GB-451667-A (GB)
Title: Improvements in automatic switches for use in telephone or like systems
IPC: H04Q3/00
Filed: 1935-02-08
Abstract: 451,667. 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. 8, 1935, No. 4183. [Class 40 (iv)] A switch of the vertical and rotary type adapted to hunt over a number of levels in succession, is re-set in a vertical direction, after finding all lines in a level busy, by a vertical hunting operation controlled by a marking dependent on the level previously hunted over. The switch shown is a doublehunting P.B.X. connector, and ground connected to one or more of the 11th contacts of the four speech wipers in each level operates one or more of the relays W .. Z to mark a vertical bank or, in the case of the last level of a group, to send a busy signal. On seizure of the switch relays A, B and C pull up and the digit is repeated to vertical magnet VM over a second winding of C, the original circuit of which is shunted down on the first vertical step. At the end of the digit C relapses and operates DR whereupon the rotary magnet RM energizes and interacts with E until, assuming an idle line in the level, one of the switching relays HA, HB operates. On the first rotary step the shunt on C is removed and C reoperates. If both test wipers find idle lines HA has preference since it opens the locking circuit of HB, operative connection between wipers P1, P2 being prevented by rectifier MRA which also prevents false switching due to presence of booster battery on the test-contacts. Relay DR relapses and brings up J which completes the ringing circuit, ringing tone being connected to the lower winding of D. When the called party replies, F pulls up and connects D to the wanted line, varying resistances of which are compensated by an ironhydrogen baretter BRA. DR reoperates and releases J to effect booster metering. When the calling party replaces his receiver, operated relays relapse to complete a self-interrupting circuit over 11 for RM which steps the switch forwardly out of the bank whereupon it returns to normal. If the calling party does not hang up, a delayed alarm is operated over lead 13. The linking of test points T by an attendant operates a buzzer over 12 if the second set of wipers is in operation. All lines in level busy. Eleventh step springs S open the circuit of E and operate RN which releases DR and connects up relays W .. Z to be operated in combination according to ground markings applied to the 11th contacts. W or X is always operated if the required group extends to a further level. The operation of RN, relapse of DR and operation of W or X causes RM to take a step to the 12 position where the switch restores and on reaching normal releases RN which makes a self-interrupting circuit for VM. The W .. Z combination marks a level in the vertical bank, and when this is reached, DR is bridged across the bank contacts, operates to open the vertical stepping circuit and the locking circuit of W .. Z. Further levels may be searched in similar manner, and if the whole of the group is busy, the switch operates the YZ combination on the 11th step of the last level of the group to connect up busy tone and flash from BT, busy hold being applied to relay B. An overflow meter is also operated over P2.