Patent GB-191409822-A (GB)
Title: Improvements in or relating to Automatic Telephone Systems.
Filed: 1914-04-21
Granted: 1915-05-27
Abstract: 9822. Aktieselskabet Elektrisk Bureau. April 22, 1913, [Convention date]. Automatic exchange systems.-In a two-wire system in which each set of interruptions of the line circuit is followed by an interruption of longer duration to produce the necessary change in the selector circuits, the line relay controls a short circuit around the slow-release changeover relay, which is so designed that it does not release its armature during the momentary short circuits, but does so during a short circuit of longer duration. Construction of selectors. The group and line selectors are of the coarse-and-fine adjustment type, in which the tens magnet M<3>, Fig. 1, rotates the contact-arms to select a group of ten sets of terminals and the units magnet M<4> selects one of such group of terminals. The contact-arms 14, 15 serve to bridge contactsegments 12, 13, individual to the selector, to the outgoing terminals. The contact-arms 14, 15 are rotated above their contacts until the test magnet M<5> is energized and depresses them. The test arm 29 normally engages its contacts. A disk P<4>, having ten notches, engages a spring f<5> so arranged that, when all ten successive units steps have been taken without finding an idle trunk, the spring falls at the eleventh step into a notch, whereby the units rotary magnet is disconnected, the further movement of the selector to its normal position being produced by the tens rotary magnet. Preliminary selector. When the subscriber A<1> removes his receiver, his line relay R' energizes over contacts 4, 5 the rotary magnet M<1>, which rotates the selector until an idle group selector is found, when the test relay M<2> is energized over its left-hand winding, test lead S', and at first over contacts 75, 23, and afterwards, when the relay R<1> is energized, over relay R<2>, and contacts 9, 76. The relay M<2> locks up over contact 11, disconnects the line relay R<1> at contacts 2, 3, and depresses the contact-arms 6, 7, so that the calling line is extended to the leads L<3>, L<4>. Group selector. The line relay R<4> is thus energized over the calling line and the springs 16, 17 of a relay R<3>, and the relay R<2>, energized over the test lead S<1>, completes the circuit of a slow-release relay R<5> over contacts 19, 21 and a resistance 20. During the short interruptions of the line circuit; the relay R<4> shortcircuits the relay R5 which has not time to release its armature. The first set of selecting-impulses is therefore repeated by the relay R<4> over contacts 23, 22, 24 to the tens rotary magnet M<3>, which rotates the contact-arms 14, 15, 29 to select a group of terminals leading to line selectors serving the wanted subscriber. The last interruption of the line circuit is long enough to enable the relay R<5> to release its armature, thus energizing, over contacts 23, 25, 26, 27, a self-locking relay R<6>, which completes the circuit of the units rotary magnet M<4> through an interrupter U<2>, thus rotating the selector until an idle line selector F, Fig. 2, is found. The test magnet M<5> is then energized over the test lead S<2>, and contacts 31, 32, and locks up over contact 64, thereby energizing a relay R', and depressing the contact-arms 14, 15 so as to extend the calling line to the line selector F. The relay R<3> (1) unlocks the relay R<6>, thus disconnecting the units rotary magnet M<4>, and (2) disconnects the relays R<4>, R<5>, so that the speaking leads L<3>, L<4> are free from anv lateral connexions. If no idle line selector is found, the notched disk P<4> shifts the springs f<5>, thus opening the locking-circuit of the relay R<6> and disconnecting the rotary magnet M<4>. Line selector. The relay R<8> is energized over the calling line, and removes the short circuit around the relay R', which energizes the relays R<9>, R<11>. The second set of selecting-impulses is repeated by.the relay R<8> over a circuit from the battery, contact 39 of relay R", contacts 41, 40, 42, 43 to the tens rotary magnet M<6>, which rotates the contact-arms to select the tens group of terminals. During the last interruption, the relay R<9> is short-circuited long enough to release its armature, energizing the self-locking relay R<10>, which substitutes the units rotary magnet M<7> for the tens magnet M<6>, so that the last set of impulses causes the selection of the wanted line. Busy test, and busy release. The armature of the slow-release relay R‹ is arranged to close its contacts 66, 67 shortly before it closes contact 65. If the wanted line is engaged, the test magnet M<8> is not energized when contact 66 is closed, so that a circuit is closed over contacts 65, 68, 69, through the lower winding of a relay R<12>, which opens at contact 48 the locking-circuit of the relay R<10>, so that when the relay R<12> is de-energized by the final long interruption, the relay R<11> is short-circuited over contacts 55, 56, 71, 72. The relay R<11> brings about the release of the connexion and gives a busy signal to the calling-subscriber as described later. Supply of ringing-current. If the wanted line is free, the test magnet M<8> is energized over a circuit from battery, through contacts 66, 50, magnet M<8>, test lead S', normal contacts of preliminary selector, and left-hand winding of test relay M<9>. The magnet M<8> depresses the contact-arms, thus connecting the ringing- generator J through the contacts 51, 52 of relay R<10> to the called line. When the called subscriber answers, the back-bridge relay R<12> is energized, thus connecting the calling and called lines at contacts 54 and opening at contact 48 the locking-circuit of relay R<10> so as to disconnect the ringing-generator. Release. If the called subscriber hangs up first, the relay R<12> closes a short circuit around relay R" over contacts 55, 56, 57, 39, thus de-energizing relay R". Similarly, if the calling-subscriber hangs up first, the relay R<8> short-circuits relay R<9>, which in turn short-circuits relay R<11> at contact 67. The relay R<11> connects an interrupter U<3> over contacts 59, 60 to the tens magnet M<6>, which rotates the selector to its normal position, when the contact 60 is opened. The relay R" also closes a short circuit over contacts 61, 62 for the test magnet M<5>, Fig. 1, of the group selector, so that an interrupter U<4> is connected over contacts 73, 74 to the tens magnet M<3>, which rotates the group selector to normal position, wherein the circuit of the relay R<3> is opened at contact 35, and the tens magnet disconnected. The test magnet M<5> also opens at contact 77 the circuit of the test magnet M<2> of the preliminary selector. If the release was initiated by the called subscriber, the relay R<1> will again be energized over the calling line, and the rotary magnet M' energized over contacts 4, 5. The connexion of the calling line to the next idle group selector is prevented by the inclusion in the circuit of the test relay M<2> of a contact 88 controlled by a latch member 90, which co-operates mechanically with the armature of the relay R' in such a way that contact 88 is opened if the relay R<1> is energized when the preliminary selector is in an off-normal position, but not otherwise. The preliminary selector is rotated nearly to its normal position, when the spring f<1> opens the motor circuit at contact 5, and the interrupter U<5> is connected over contact 82 to a third winding of the relay R', thus giving the calling subscriber a tone signal indicating that the called subscriber has replaced his receiver. When the calling-subscriber hangs up, his line relay again energizes the magnet M', moving the selector to normal. In the case of an attempt to call a busy line, the relay R" brings about the release of the selector and connector as described above, and moves the preliminary selector to the position in which the busy interrupter U<5> is connected to the calling line to give a busy signal. The release is completed when the subscriber hangs up.