Patent GB-378587-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1931-06-13
Abstract: 378,587. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and PATTERSON, W. G., 68, Eltham Road, Lee, both in London. June 13, 1931, No. 17235. [Class 40 (iv).] In a single-motion group selector which has double-ended wipers the ends of which come into engagement with corresponding rows of terminals in turn and which is controlled by marking from a common control circuit, each setting of the marking switch marks two, groups accessible over opposite ends of the wipers, and if the later group is the one required the marking is not made effective until after the earlier group has been passed over. In Fig. 1, the pairs of groups denoted by the digits 1 and 6, 2 and 7, &c. are marked in common, the marking circuit if the digit is 6-0 being effective only after five groups have been traversed. The selector in Fig. 2 is selectable in response to either of two digits at the preceding selecting stage and a discriminating signal therefrom causes a call to be routed over one or other of a pair of groups. Such a system is described in Specification 378,585. Instead of a discriminating signal being received, the selector may be arranged to be seized over one or other of two routes of access. First arrangement, Fig. 1. Upon seizure of the selector, the associating relay K(I) operates, and line relay A energizes over the loop, connecting up release relay B and dialling relay C(I). Relay K(II) locks, while relay JB opens the initial circuits of the relays such as K in all the selectors of the group. Impulses are repeated to the magnet DSM in series with dialling relay C(II), which falls back at the end of the train and close the stepping circuit for the magnet SM. If the digit received is not greater than 5, relay PP(I) operates at once over wiper DS2 and completes the marking circuit over wiper DS3, so that test relay T energizes over the test and marking wipers SC, M of the selector when an idle trunk is found in the marked group accessible over the full line wiper ends. If however the digit is greater than 5, relay PP(II) operates over a shaft contact osn when the full line wiper ends have made a complete traverse and locks, thus enabling an idle trunk to be selected in the marked group accessible over the dotted line wiper ends. If no idle trunk is found in the wanted group, a circuit is closed over the effective end of the test wiper SC in its last position for relay T in series with relay LC, which sends back a busy signal. Second arrangement, Fig. 2. The shaft of the selector is rotated by a pair of magnets DM1, DM2 which operate alternately as long as a sprag magnet SM is energized and control a rotary armature. Discrimination depends on a relay P which energizes in series with line relay A when earth is not connected to the b wire at the preceding selecting stage, and connects up relay PP(I). Impulses are received as in Fig. 1, and diallir.g relay C on falling back energizes the sprag magnet SM to start the selector. If relays P, PP(I) are operated, the marking circuit is closed over wiper DS3 to enable an idle trunk to be selected in the marked group accessible over the full line wipers. If however relays P, PP(I) are not operated at this time, relay PP(II) operates over a shaft contact osn and locks, thus enabling an idle trunk to be selected in the marked group accessible over the dotted line wipers. It will be seen that each pair of groups is marked in response to either of two consecutive digits. Accordingl.y a discriminating signal is sent forward when the digit is odd by the connection of earth to the b wire over wiper DS2.