Patent GB-191414808-A (GB)
Title: Improvements in or relating to Telephone Systems.
Inventor: BURFEIND RAYMOND HENRY
Filed: 1914-06-19
Granted: 1915-06-17
Abstract: 14,808. Burfeind, R. H. June 21, 1913, [Convention date]. Automatic and semi - automatic exchanqe systems.-To enable a Strowger two-coordinate selector to select an idle line of a large group of lines occupying more than one level of its terminal bank, arrangements are provided by which the selector in the course of its vertical movement can test whether there is an idle line in the level to which it has been raised, so that after being set on the lowest level of the group, it continues its vertical movement if all the lines in that level are engaged, until it finds a level in which an idle line is available. The invention is applicable to group selectors, in case, for instance, it is desired to allot more than the usual ten connectors to the service of a given group of lines, and also to rotary connectors having large groups of lines leading to private branch or other manual exchanges. Both these applications are illustrated in the system shown in Figs. 2 and 3. The connector H, Fig. 3, belongs to a group of 40 connectors, of which the 4th, 5th, 6th, and 7th levels are allotted to a private branch-exchange, and these 40 connectors are multipled in the 4th, 5th, 6th, and 7th levels of the selectors E, Fig. 2. The vertical testing movement of the selector E is controlled by an auxiliary wiper 72 engaging terminals 71<a>, which are connected to ground if all the lines in the corresponding levels are engaged. The grounding of the terminals 71<a> is effected as follows. When a line is engaged by a selector, a corresponding pair of terminals in an auxiliary multiple bank a of the selector are connected together by an auxiliary pair of bridging-wipers 71. The upper terminal of each pair in the bank a is connected to the lower terminal of the next pair to the left, and it will be seen that when all the lines in a given level have been engaged by selectors, a ground connexion is established through the terminals a and the bridging-wipers 71 to the test terminal 71<a> of the busy level; but as long as any line in the level is disengaged, this ground connexion is incomplete. The terminals a in the uppermost level of each group are not interconnected in this manner, so that when a selector is raised to the uppermost level of a group, its vertical movement is arrested, even if all the lines in the level are engaged. It will be seen that the 1st, 2nd, and 3rd levels of the selector E, Fig. 2, are each allotted to a separate group of ten connectors, while the 4th, 5th, 6th, and 7th levels are allotted in common to a group of 40 connectors, and the 8th, 9th, and 10th levels are allotted to a group of 30 connectors. The vertical testing-movement of the connector H is controlled in the same way as that of the selector E. Line switch C and master switch D, Fig. 2. These operate as described in Specification 1419/10 to extend the line of a calling subscriber to an idle selector E. First selector E, Fig. 2. To obtain a connexion with the private branch exchange occupying the 4th, 5th, 6th, and 7th levels of the connectors H, the subscriber must transmit the number 441. The line interruptions of the first digit are transmitted in the usual way by the line relay 30 to the vertical magnet 28, which raises the selector to the 4th level. A slowrelease relay 35 is energized in series with the vertical magnet at the first impulse and energizes a relay 66, which locks itself up. At the conclusion of the series of impulses, the relav 35 de-energizes, and if there is an idle line in the 4th level, a self-interrupting circuit is closed for the rotary magnet. If, however, all the lines in the 4th level are engaged, the deenergization of the relay 35 closes a self-interrupting circuit for the vertical magnet 28. This circuit extends from the vertical test wiper 72 (which is now in engagement with a grounded terminal 71<a>, as explained in the first paragraph of this abridgment) through an interrupting- relay 105 and a slow-release relay 106. The selector is thus raised to the 5th level, and, if necessary, it may be raised again to the 6th or 7th level. While this vertical hunting-movement continues, the circuit of the rotary magnet 29 is held open by the relay 106; but when a level comprising an available line is found, the relay 106 de-energizes and a self-interrupting circuit is completed for the rotary magnet. Every time the rotary magnet energizes, it opens, at the contacts 59, 60, the original locking-circuit of the relay 66; but as long as the wipers are on the terminals of busy lines, the relay 66 is kept energized by a circuit through the test wiper 26. When an idle line is found, the relay 66 de-energizes. The de-energization of this relay opens the circuit of the rotary magnet and completes the circuit of a switching- relay 58, which disconnects the incoming line from the line relay 30 and connects it through the wipers 25, 27 to the line relay 47, Fig. 3, of the selected connector. The original circuit of the relay 58 is opened, after a moment, by the de-energization of the relay 34; but in the interval, a holding-circuit for this relay and for the winding 12 of the line switch C is provided by the energization of the connector relays 47, 100. Connector H, Fig. 3. The line interruptions of the second digit are transmitted by the line relay 47 to the vertical magnet 39, which raises the connector to the 4th level. A slow-release relay 74 is energized in series with the vertical magnet at the first impulse and energizes the private magnet 45. At the conclusion of the series of impulses, the relay 74 de-energizes, and if there is an idle line in the 4th level, the private magnet 45 also de-energizes, and the side switch moves to its second position. If, however, all the lines in the 4th level are engaged, the private magnet 45 is kept energized by a relay 108<a>, which is energized through the vertical test wiper 72<a>, and a circuit is also closed by the relay 108<a> through an interrupter relay 114 and the vertical magnet 39, so that the vertical movement of the connector is continued until a level is found in which an idle line is available. The relay 108<a> then deenergizes, and the side switch moves to its second position. The single line interruption representing the 3rd digit operates the rotary magnet 40 to move the wipers of the connector to the terminals of the first line in the selected level. If this line is free, the private magnet 45, which was energized by the relay 74, becomes .de-energized again a moment later and permits the side switch to move to its third position, but if the line is engaged, a relay 121 is energized through the test wiper 37, and this relay, in addition to closing a holding-circuit for the private magnet, completes a second circuit for the rotary magnet 40, so that the connector is moved to the next set of terminals. The circuit closed by the relay 121 through the rotary magnet includes the back contact of a relay 131, which is energized by the closure of the contact 124 controlled by the rotary magnet. By this arrangement, the energization of the rotary magnet is rendered intermittent, and the rotary movement is continued until an idle line is found. The relay 121 then de-energizes, opencircuiting the rotary magnet and de-energizing the private magnet 45, so that the side switch moves to its third position. Busy signal. The last line in the top level of a group has a pair of test terminals strapped together, as in the case of single lines described below, so that if all the lines to the private branch-exchange are busy, the connector, on arriving at this last line, sends hack a busy signal to the calling subscriber. The way in which this is effected is described in the concluding paragraph of this abridgment. Supply of ringing-current. In the third position of the side switch, ringing-current is supplied to the selected line by the intermittent energization of the relay 49 until the called subscriber replies, the ringing cut-off relay 162 being then energized by the back bridge relay 48. Release. The connector release magnet 46 is energized by the de-energization of the relays 47, 100 when the calling subscriber hangs up his telephone, and the holding-circuit for the selector E and line switch C is opened at the contact 75. The de-energization of the relay 58 completes the circuit of the selector release magnet 31. Selecting single lines. Certain levels of the connector may be allotted to ordinary single lines. To enable the connector to fulfil the ordinary testing-functions with regard to these lines, so that if the wanted line is busy it does not pass automatically to the next line, as in the case of groups of lines, it is provided with an additional test wiper 37<a> connected to a busy relay 120. In the case of lines belonging to a group, the terminals engaged by the wiper 37a are blank and inoperative; but in the case of single lines, they are strapped to the terminals engaged by the other test wiper 37, so that if the wanted line is busy, the relay 120 is energized as soon as the relay 74 de-energizes at the termination of the final series of impulses. In this case, the relay 120 locks itself up, opens the circuit of the rotary magnet 40 (so as to prevent it from being energized by the relay 121), locks the private magnet 45 (so as to keep the side switch in its second position), and connects the busy signal 0 to the calling line.