Patent GB-795128-A (GB)
Title: Improvements in or relating to circuit arrangements for setting group selectors in tele-communication and especially telephone installations
IPC: H04Q3/00
Filed: 1955-02-23
Abstract: 795,128. Automatic exchange systems. SIEMENS & HALSKE AKT.-GES. Feb. 23, 1955 [Feb. 23, 1954], No. 5489/55. Class 40 (4). A group selector is set to a wanted group by means of marking applied to the starting and end positions of the group; if the selector, on hunting, finds all outlets of the group engaged, it steps forward again into the starting position of the group. During the selector's passage over unwanted groups, its testing circuit is disconnected. The starting and end positions are rest positions between the groups, the end position of one group being also the starting position of the next group. As shown, the group selector RW is a motor-driven 100-step rotary switch, making 4-wire connections over wipers a, b, a1 and b1 and having auxiliary wipers c, d, e and f. Relay C operates on the seizure of the selector, and relay A repeates incoming dial impulses to magnet WR which steps the marker switch wipers WR I and WR II accordingly. At the first step, off-normal contacts wroI and uroII are actuated and relays D and B are energized. This causes the simultaneous energization of the two motor magnets M1 and M2 of the group selector RW which is thereby held stationary. At the second step of the marker switch WR, relay B is released, and the magnets M1 and M2 are energized alternately in known fashion by means of cam contacts ml and m2 controlled by the shaft of the selector which is thus driven in pursuit of the marker switch, actuating offnormal contacts n1, n2 and n3. When wiper f reaches the contact marked by wiper WR I, relay B is re-operated so that the selector is stopped by the energization of both magnets Ml and M2 together. At the end of the dial impulse train, relay A. has finally released and is followed after a delay by relay D. If there is a free outlet in the wanted group, a group busyrelay such as G1 is energized through one of the contacts cna &c. of the " busying relays " (not shown) of the outlets. The relapse of relay D therefore completes a circuit over wiper e for relay U which operates, releasing relay B and re-operating D to start the selector motor and complete a test circuit over wiper c. Relay U holds on its winding II. When the selector finds an idle outlet, test relay P operates, energizing both magnets M1 and M2 to stop the switch and releasing relays D and U. If, however, the selector fails to find an idle outlet, it steps to the end position of the group, marked in bank f by means of marker switch wiper WR II. This marking energizes relay B, which stops the selector, operates a statistical meter ZR via wiper d, and releases relay U so that B is released again and the selector steps on. Since U is not energized, the test circuit over wiper c is broken and the selector passes over all the remaining groups to the starting position of the wanted group, marked by wiper WR I, where relay B operates to stop the selector and release relay D. When an outlet in the group becomes idle, the group busy relay such as G1 is energized to bring up relay U which starts the selector hunting again by releasing relay B and operating relay D. In modifications, Figs. 2, 3, and 4 (not shown), the selector is arranged to hunt over more than one group at a single setting and the sequence of groups in the selector contact banks may be changed.