Patent GB-148971-A (GB)
Abstract: 148,971. Ges. f³r Elektromechanische Telephonapparate. Jan. 10, 1914, [Convention date]. Automatic exchange systems. -In a system in which connexion is temporarily made with a calling line by one of a small number of quick-acting finders, which is released after connexion has been made with the same line by one of a larger number of slow-acting finders, the test circuits are arranged so that a slow-acting finder which has been started in search of a particular calling line cannot be brought to rest on the terminals of any other line which calls simultaneously. Each idle quickacting finder F1, F2, F3 is associated with an idle slowacting finder LF1, LF2, &c., by a pre-selecting switch VS1, VS2, VS3, and when a call arrives the first idle quick-acting finder and the slow-acting finder with which it is for the moment associated are started simultaneously. The quick-acting finder is a two-coordinate selector, consisting of main and brush-choosing switches in series, and is set on the calling line under control of tens and units guide-wires. The slowacting finder is a one-coordinate switch and is set on the calling line under control of a, test-circuit which extends through the associated pre-selecting switch and quick-acting finder. For this purpose the slow-acting finder has an auxiliary test wiper for each quick-acting finder; the terminals engaged bv the wiper d<1>f, for example, are multipled in the bank of F1 but not of F2 or F3, and the terminals engaged bv d<2>f are multipled in F2 but not in F1 or F3. The line relay l00 of a calling line energizes a starting-relay FS, which sends a transitory impulse over a starting-wire St to the first idle quick-acting finder, say F1. This impulse energizes the magnets E1, E<1>1 of the main and brush-choosing switches, and is also conveyed over a circuit 201, 207, Fig. 2, to the magnet 214 of the slow-acting finder LF1 (which has been associated bv the switch VS1 with the finder F1), this branch of the starting-circuit being completed via 208<a>, 202<a>, 216, Fig. 2. The finders L1, LF1 leave their normal positions and the off-normal switches OS1, OS2 connect the magnets E1, E<1>1, 214 to interrupter circuits to continue the rotation of the switches. The switch OS1 also extends the starting-circuit St to the next finder F2. When the main and brush-choosing switches of the finder F1 have been brought to the required positions, the circuits of magnets E1, E<1>1 are opened bv relays tp, sp, which are energized over tens and units guide-wires o, o<1> grounded by the line relay l00. The relays tp, sp jointly close a circuit for the relay CR, Fig. 2, which locks itself in series with the cut-off relav co00 which de-energizes the line relay l00 and starting-relay FS, so that further calls can be dealt with. When the slow-acting finder LF1 arrives at the terminals of the line already found by the quick finder F1, the circuit of its magnet 214 is opened by a relay 220, Fig. 2, which is energized in a circuit 202, 208, d<1>f, d<1>00 and the fourth wipers of the finder F1. The possibility of the continued energization of the magnet 214 at this moment through another switch such as VS2, which might happen to be wiping over contacts multipled to those occupied by the switch VS1, is obviated by a contact 610<1>, which is held open as long as the switch VS2 is in motion. The further operation of the system is the same as described in Specification 28502/13.