Patent GB-191878-A (GB)
Abstract: 191,878. Pollak, J. E., (Siemens & Halske Akt.-Ges.). Nov. 2, 1921. Automatic exchange systems.-Relates to systems for small exchanges in which the calling and wanted lines are connected by pre-selectors to the same trunk, the wanted line being selected by a temporarily used numerical switch. In one system, the trunk line taken into use by the calling line is alone made accessible at its test lead to the pre-selector of the wanted line, all other trunks being rendered inaccessible until the numerical switch is released. Each subscriber has a special key to release the connection independently of the other. The wanted line is rung by a further operation of the calling dial. In a second system, several speaking routes can be established simultaneously by the use of circular test circuits including, in the setting route, individual sources of current. In a third system, two pre-selecting stages are used. In other systems, the second pre-selector stage includes a number of pre-selectors connected in parallel and having access to different groups of trunks. First system, Fig. 1, in which the calling and called lines N1, N2 have access through their pre-selectors VW1, VW2 to the same trunks, such as a10, b10, c10, the wanted lines being selected by connectors LW1, LW2 connected to the trunks a10, b10, c10 by call-finders AS1, AS2. Connection to idle connector LW1, Fig. 1. When the subscriber N1 removes his receiver, the rotary magnet D1 energizes over the calling line, and contacts f45, f35, moving the wipers to their first contacts, after which the magnet D1 is energized over wiper o13 under control of relay T1. When an idle trunk a10, b10, c10 is found, relay T1 energizes over contacts f35, f45, the calling line, wiper o12, resistance c20, and contacts s20, b21. Relays A20, V20 energize, relay A20 energizing the rotary magnets D30, D40 of finders AS1, AS2. If all the finders are in use, busy current is connected to the calling line over the third winding of relay A20. When the calling trunk is reached by finder AS1, say, relay P3 energizes over o31, s21, R(I), a23, t20, v21. Relay T20 stops the other finders. Selection and test of wanted line. The tens and units selecting-impulses are repeated by relay A20 to the lifting magnet H30 and rotary magnet D39, and the series relay U then connects the test relay Y over wiper o33 to the lead e4 of the wanted line. Establishment of speaking route. If the wanted line is free, relay Y energizes relay F3, which (1) opens at f35 the normal test circuits of the pre-selectors, (2) energizes a relay B20 to disconnect battery from the test leads c11 &c. of all idle trunks, (3) at contact 30 connects battery over a relay S direct to the test lead c10 of the trunk taken into use by the calling line, thus short-circuiting the resistance c20 and increasing the potential on the lead sufficiently to enable the pre-selector of the wanted line to stop on this trunk, (4) energizes a relay U4 of connector LW2 to prevent interference, and (5) closes a circuit over wiper o34, lead e3, for the rotary magnet D2 of the pre-selector VW2 which rotates until it finds the trunk a10, b10, c10. The release magnet M31 energizes over contacts g32, y32, and restores the connector and its circuits. The connector is also released, if it remains too long in use, by a time switch ZS1. Ringing current. The calling subscriber again operates his dial, thus altering the voltage at the terminals of the feed bridge X20, A20, thereby charging and discharging the condenser in the ringing circuit at the called station. Release. When both subscribers hang up, relays A20, V20, S de-energize, opening all circuits. Either subscriber may release by depressing a key t<1>, thereby causing the differential relay X20 to open the circuit of relay V20. Second system, Fig. 2, in which several calls may be set up simultaneously by the use of circular test circuits including, in the setting route, individual sources of current. Connection to idle connector LW22. When a subscriber removes his receiver, the test relay T21 momentarily energizes over the calling line and closes the circuit of the rotary magnet D21 which rotates the pre-selector VW21. When an idle trunk is found, the test relay T21 energizes over the test wiper and stops the switch. Relays A21, V21 energize as in Fig. 1 and cause a call-finder AS22 to connect up an idle connector LW22 which is set as before on the wanted line. Test of wanted line and establishment of speaking route. If the wanted line is free., the relay P23 energizes over wiper o27, lead e7, and normal contact d22, and connects earth over wiper o28 and lead e6 to start the pre-selector VW22 which rotates until relay T22 energizes over the circular route including wiper o24, transformer winding Tr, relay RC, wiper o29, and lead e5. Relay RC causes relay V22 to energize the release magnet M22 to restore the connector and its circuits. The relays S20, S21 associated with the trunk VL21 were energized when the wanted line tested free. The preselectors are restored to normal when both subscribers hang up. Third system, Figs. 3 and 3<a>, in which first and second pre-selectors are used, the ringing-source being associated with the second pre-selectors. Connection to idle connector LW31. A calling line is connected in the usual way by preselectors IVW31, IIVW31 to an idle trunk VL31 to which a call-finder AS31 connects an idle connector LW31 which is set on the wanted line as before. Test of wanted line and establishment of speaking route. If the wanted line is idle, the test relay P32 is energized over wiper o37, lead e37, and resistance w34, and momentarily earths wiper o38 and lead e36 to energize the line relay R33, which locks up under control of relay T35, so that the pre-selector IVW32 rotates to find an idle second pre-selector, which in turn is rotated by magnet D36 to find the trunk VL31 whereupon relays T36, RC30 are energized in a circular test route including wiper o38 and lead e36. Ringing-current. The relay U32, which was energized ever lead e36, connects the generator UN to the called line. When the subscriber replies, relay L30 disconnects relay U32, which connects the called line through to the feed relays A, X. Fourth system, Figs. 4, 4a, 4b, in which three second pre-selectors IIVW1, IIVW2, IIVW3 in parallel have access to three groups of trunk lines. Connection to idle connector LW41. The preselector IVW, acting as in Fig. 2, connects the calling line to the three pre-selectors, relay R40 earthing the rotary magnets D41, D42, D43 which are energized in turn by the commutator UN41. The test relays T41, T42, T43 are earthed in turn by the commutator UN42. When an idle trunk VL41, say, is found, the corresponding test relay T41 disconnects relay R40 and switches the calling line through to the feed relays A40, X40, whereupon a finder AS41 connects up a connector LW41 which is set as before on the wanted line. If all the setting- routes of a group of trunks are engaged, a relay G40, Fig. 4<a>, is energized over contacts of the test relay P40, P41, &c. and opens at contact 409 the test circuits of that group of trunks, thereby preventing the selection of a trunk unable to extend the call. In an alternative system, the circuit of the rotary magnets is opened by the relay G40. Test of wanted line and establishment of speaking route. If the wanted line is free, relay P42 energizes over wiper 423 and lead 424 and connects earth over wiper 429 and lead 430 to energize the test relay T45 to start the first preselector IVW1, which rotates under control of relay T45 to find an idle set of second pre-selectors. Relay R41 connects up the rotary magnets D46, D47, D48, and also energizes a relav U41 over leads 443, 438, and wiper 437 in series with a relay F41. Relay U41 locks up, disconnects the test relays T46, T47, T48 from their respective test wipers and connects them all to the fourth wipers of the pre-selector and to lead 443 which is connected over lead 438 and wiper 437 to the middle point of a differential relay DR41, collected to battery by relay P42. Winding I of relay DR41 is connected to the fourth lead 455 of the trunk VL41 so that when the pre-selector IIVW41, say, reaches the trunk VL41, winding I of relay DR41 is short-circuited over wipers 453, 456, 440, 437, and the relay DR41 energizes, completing a circuit from battery over commutator UN41, lead 461, relay G41, lead 455, relay T46, lead 462, and commutator UN42. Relay T46 stops the pre-selector IIVW41, disconnects relay R41, and switches the called line through to the trunk VL41. Fifth system in which two pre-selectors in parallel have access to two groups of trunk lines. Only that second pre-selector associated with the wanted line is operated which has access to the trunk taken into use by the calling line. A polarized relay associated with the two second preselectors brings one or other into operation according to the group of lines with which the temporarily used connector is associated. The test circuit is similar to that shown in Fig. 2. Sixth system in which the trunk taken into use by the pre-selectors is provided with separate feeding bridges for the calling and called subscribers. The trunks are connected twice to each pre-selector, the two sets of terminals being accessible respectively to calling and called lines. As before, a connector is connected by a finder to the trunk taken into use by the calling line and is set on the wanted line, a circular test circuit similar to that shown in Fig. 2, but including a fourth wiper of the pre-selector, being used to establish the speaking route. The rotarv magnet of the pre-selector is supplied with current from the connector and is controlled by a relay of the connector instead of by the subscriber's cut-off relay. The ringing-apparatus is associated with the trunks. Each subscriber ca