Patent GB-191517581-A (GB)
Title: Improvements in Automatic Telephone Call Distributing Systems.
Filed: 1915-12-16
Abstract: 17,581. Western Electric Co., [Assignees of Craft, E. B., and Reynolds, J. N.]. Dec. 19, 1914, [Convention date]. Semi-automatic exchange systems.-In a semiautomatic system, a calling-line is first automatically connected to an idle operator and subsequently to a connecting-circuit to which this operator has access. This is effected by a single switch of the kind in which one of a number of sets of brushes is released so as to move over a corresponding group of terminals. The brush-choosing spindle is provided with a set of wipers which select an idle operator, the tripping-members on this spindle being arrested in such a position that, during the subsequent movement of the brush carriage, the particular set of brushes released corresponds to a level of terminals of connecting-circuits on the position of the selected operator. A switch of this kind may also be used as a line-finder for a large group of lines divided into sub-groups, each subgroup of lines being connected to terminals in a certain level; the process of connecting to a calling-line thus consists in releasing the particular set of brushes serving the sub-group containing the calling-line and then rotating the brushes to find this line. In the system described a calling-line is connected through a line-finder A, Fig. 1, to a switch B, Fig. 2, which makes a preliminary connexion over the brushes 65, 66, 67, carried by the brush-choosing trip-spindle 61, to an idle operator, and subsequently a connexion over the brushes 79 .. 82, to a connecting-circuit C, Fig. 3, which may terminate in a numerical selector or a plug for extending the call in known manner. The operations in further detail are as follows: - Operation of line-finder A, Fig. 1. When a subscriber removes his receiver, his line relay 7 puts a selectable potential upon the test terminals 42 of the finders, and a relay 6, common to all the lines in a particular level, connects battery to a terminal 21 in the path of a brush 20 carried by the brush-chooser 19. The relay 6 also moves the sequence switch 100 into its 2nd position, energizing the clutch magnet 16 of the brush-chooser 19, which rotates until the brush 20 engages the terminal 21, when the test relays 28, 29 are energized, and the sequence switch moved into its 4th position. Proper centring of the spindle 19 is effected by a shunt circuit for the magnet 16, comprising a contact 14 and arm 15. In its 4th position, the sequence switch 100 energizes the clutch magnet 43 to rotate the brush carriage. As the brushes pass the spindle 19, the set corresponding to the level containing the calling-line is released, and the brushes continue to rotate until this line is found, when a circuit is completed over brush 40 and relays 28, 29. Relay 28 brings in its low-resistance winding 31 to prevent other finders from seizing the calling-line, and relay 29, as soon as the brushes are properly centred and the shunt over contact 114 and interrupter 24 is removed, opens the circuit of the clutch magnet 43 and moves the sequence switch. 100 into its 5th position, in which the cut-off relay 9 is energized to disconnect relays 6, 7, and the starting-circuit 13 is extended over contact 102 to the next line-finder. Operation of switch B, Fig. 2, to select idle operator and idle connecting-circuit. A passing contact 106, Fig. 1, made by the sequence switch 100, moves the sequence switch 200 into its 2nd position, energizing the clutch magnet 69 of the brush-chooser 61, which rotates until the brush 65 engages the test terminal 68 of an idle operator, when the test relays 64, 63 are energized and the sequence switch 200 moved into its 4th position. The relay 74, Fig. 3, lights a call lamp and moves the operator's sequence switch 300 into its second position, thereby connecting the operator's telephone set over contacts 303, 304 and wipers 66, 67, to the calling-line. In its 4th position, the sequence switch 200, Fig. 2, energizes the clutch magnet-77 to rotate the brush carriage 78. As the brushes pass the spindle 61, the set corresponding to the level containing the terminals of connecting-circuits accessible to the selected operator is released, and the brushes continue to rotate until an idle connecting-circuit is found, when the test relays 63, 64, are again energized to disconnect the clutch magnet 77 and move the sequence switch 200 to its 5th position. In this position, the calling-line is connected over contacts 210, 211 and brushes 79, 80 to the repeater of the connecting-circuit. The relay 85, Fig. 3, which energized in series with the test relays 63, 64, has moved the sequence switch 400 to its second position, so that the operator's speaking set is now connected over contacts 305, 306 and 404, 405 to the wipers 79, 80 and the calling-line. In the second position of the switch 400, a contact 407 earths the brush 82, energizing the release control relay 90, Fig. 2, which moves the sequence switch 200 to its 6th position, thereby closing contact 214 so as to move the sequence switch 100, Fig. 1, to its 6th position also. In the 5th and later positions of the sequence switch 200, Fig. 2, the clutch magnet 69 of the brush-chooser is energized to return the spindle 61 to its normal position, thus breaking the connexion over the brushes 66, 67 with the operator. When the operator has learnt the desired connexion, she depresses the listening cut-off key 95, Fig. 3, thereby moving the sequence switch 400 into its third position and returning the switch 300 to normal, so that the operator tests idle to further calls. The operator then sets up the connexion in known manner. Release. At the end of a conversation, the supervisory relays 96, 97 light up the associated lamps, and the operator presses the release key 98, which returns the sequence switch 400 to its initial position, thereby opening the circuit of the release control relay 90, Fig. 2, which moves the sequence switch 200 to its 7th position, a circuit being closed over contact 216 to move the sequence switch 100 into its 7th position. In the 7th position of the switch 200, the brush carriage 78 is returned to normal, whereupon the brush 250 energizes the relay 63 and moves the switch 200 to its initial position. Similarly in the 7th position of the switch 100, the brush carriage of the line-finder is returned to normal, when the brush 38 energizes the relay 29 to arrest the brush carriage and move the sequence switch to its 8th position, in which it remains until the sequence switch 200 reaches normal and closes a circuit over contact 216 to move the switch 100 to normal. Indicating number of calling-line to exchange operator. Banks of lamps 152, containing a lamp 151 individual to each subscriber, are arranged within sight of the operators, who may flash the lamp of the calling-line by depressing a lamp-flashing key 93, Fig. 3, which increases the current through a relay 94, Fig. 1, sufficiently to energize this to complete the circuit of the corresponding lamp 151. This feature forms the subject-matter of the divided Specification 101,033. Removing busy test from calling-line without breaking down connexion. If the operator depresses a cut-off release key 92, the cut-off relay 9, Fig. 1, is de-energized, and the busy potential on the test terminal 50 is removed, so that the subscriber can receive a call. Metering. A key 150, when depressed, connects a source of current of a particular strength or character to actuate a message register.