Patent GB-366596-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1930-11-07
Abstract: 366,596. Automatic exchange systems. AUTOMATIC TELEPHONE MANUFACTURING CO., Ltd., Strowger Works, TAYLOR, R., 30, Oulton Road, and BEALE, C. E., 59, Towers Road, both in Wavertree, all in Liverpool. Nov. 7, 1930, No. 33581. [Class 40 (iv).] A metallic circuit is completed through a final selector with a common control circuit on the relapse of the K relay in response to the operation of a ring trip relay in the common circuit. The invention is described with reference to a double wiper final selector, Figs. 1 and 2, arranged to hunt over two or more levels successively, a final selector, Figs. 3 and 4, giving access over one set of wipers to individual lines and over the other to P.B.X. lines, the set to be effective being determined by the route of access to the switch and a 200-line final selector. Figs. 5 and 6 (not shown), similar to that shown in Figs. 3 and 4 except that it gives access only to individual lines over both wiper sets. Double hunting switch, Figs. 1 and 2. The common impulse relay A and the K relay are operated in series over the talking circuit and are followed by B, C. At the end of the (only) digit, which is repeated to the vertical magnet VM, the relapse of C energizes DR, whereupon E pulls up and energizes the rotary magnet RM. If both lines are busy, both switching relays HA, HB are short-circuited and E interacts with the magnet to cause a further step. If the whole level is busy, eleventh step relay S energizes RN which locks and energizes the rotary release magnet RZ and relay VS. When the rotary normal position is reached, RN is released and releases VS, H an impulse thusbeing given to the vertical magnet. While VS is operated, E is short-circuited, but when VS falls, interaction between E and the rotary magnet is resumed. When an idle line is found, HA or HB operates, locks and connects up ring-back tone, HA alone being locked if both lines are idle. Wiper changing relay WS, which is operated in series with HB, locks up also. E, DR fall back and the ringing circuit is completed. When the called party replies, F pulls up followed by BS, D, the last-mentioned connecting battery to the lower talking wire to give the reply signal. A, B in the common circuit are released and K then falls to complete the talking circuit and free the control circuit. If all the lines in a group are busy, HA is operated by battery on the eleventh terminal. RN, BS operate but the relapse of E instead of energizing the rotary release magnet sends an impulse to the overflow meter, and busy tone and flash is connected up. Double wiper switch hunting over one set only, Figs. 3 and 4. Relays 1A, 1K, 1B, 1C are operated in the same way as the corresponding relays in the switch just described. At the end of the first digit, 1E switches the impulse circuit to the rotary magnet 1RM and re-operates 1C. At the first operation of the rotary magnet, RN pulls up and locks. At the end of the second digit, if the switch was seized over the lower trunk and consequently 1WS is energized, and if the second digit is that of a busy first line, HS is operated over the extra bank 35 on the relapse of 1C and when, shortly afterwards, 1E falls back, 1RM is again energized in series with 1C, and re-energizes 1E which releases the magnet and 1C and then falls back. In the interval between the relapse 1C, 1E the test circuit over H is made and if the line is busy the switch takes another step. If the whole group is busy the switch is stopped owing to the relapse of HS when the extra wiper 35 moves to the blank position at the end of the group, and BB connects up the busy signal. If a P.B.X. line other than the first of a group is called, HS is short-circuited over the trailing extra wiper or if the switch is seized over the upper trunk and WS therefore is unoperated, there is no circuit for HS and in both cases BB sends back a busy signal as soon as 1E falls if the line is busy. If it is idle, or when an idle line is found, H pulls up on the relapse of 1C, releases HS if necessary and completes a ringing tone circuit. On the relapse of 1 E, a ringing circuit is completed. When the called party replies IF energizes 1BS and the connection is completed and the control circuit is freed by the relapse of 1A, 1B, 1K. If a spare number is dialled, 1F is operated at once but not 1D. The subscriber hears a special tone connected to unallotted speech terminals. Specification 366,469 is referred to.