Patent GB-191202743-A (GB)
Title: Improvements in Automatic and Semi-automatic Telephone Circuits.
Filed: 1912-02-02
Granted: 1913-02-03
Abstract: 2743. Siemens Bros. & Co., [Siemens & Halske Akt.-Ges.]. Feb. 2. [Addition to 2320/12.] Automatic and semi-automatic exchange systems.- Relates to systems of the kind described in the parent Specification in which a local connexion is interrupted, by circuit changes brought about by a trunk or other operation, in favour of a trunk or other preferred call. According to the present invention, the line of the required subscriber is tested before the connexion is made as to whether it is disengaged, or in what manner it is engaged, by connecting the test lead successively to different testing-circuits. One or other of four tone signals is given to the testing-operator according as the line tested is disengaged, engaged in a trunk call, or engaged as a calling subscriber, or as a called subscriber, in a local connexion. Selection of the wanted subscriber. The trunk operator's impulse-sender is represented by the keys 3, 4, of which the key 4 earths the b-lead continuously while the key 3 intermittently earths the a-lead. Assuming that an idle connector has been found by the group selectors G, W, the relay C is energized over the test leads c, 14, and by closing a contact 31 throws its winding 19 into the test lead circuit, thus marking the connector busy, and also connects the battery 18 to the relays A, B, and to the vertical and rotary magnets H, D, and side - switch magnet S. After the relay A has repeated the first set of selecting-impulses to the vertical magnet H, the release of key 4 causes the relay B to de-energize the magnet S, the sideswitch moving into its second position. The last set of impulses are then repeated to the magnet D, after which the side-switch moves into its third position. Busy tests. To test the required line, the trunk operator depresses a key 5, thereby energizing the relay B, which completes a circuit for the relay P<1> from the battery 18, through a resistance 40, arm 30, relay P', arm 29, and contact 32 to earth, this circuit being connected to the test wiper c<1> at the point 41. If the desired subscriber is disengaged, the cut-off relay 42 energizes in series with the relay P<1>, which closes a contact 43 so as to move the side-switch into its fourth position, from which it at once passes into the fifth position. In the fourth position, the relay P<2> is substituted for the relay P<1> and locks up over its winding 46, disconnecting the relay P<3> which would otherwise be energized when the switch reaches its fifth position. The side-switch remains in the fifth position as long as the key 5 is depressed. and the operator receives a " disengaged " signal from the buzzer 54 which is inductively connected over the contacts 60, 24, 53 to the relays A, B. The release of the key 5 de - energizes the relay B, the magnet S receiving an impulse over the contact 44, and then over the contact 58, so as to move the side switch into the seventh or conversation position. The test lead is directly earthed over the armature 37 so as to mark the line as engaged by a trunk call. If the wanted subscriber is engaged in a trunk call, the test lead being directly earthed, the relay P<1> is short-circuited in the third position of the side-switch, so that the side-switch does not advance beyond this position, and the operator receives a distinctive signal from the buzzer 57. If the wanted subscriber is engaged in a local connexion, the potential of his test lead is such that the relay P<1> is energized, and causes the side-switch to move into its fourth and fifth positions as before, but in the fourth position the relay P<2> is not energized, so that the relay P<3> is connected to the test lead in the fifth position. If the desired subscriber is himself a calling subscriber, his test lead is open at the contact 34, so that the relay P<3> is not energized, and the buzzer 56 is connected to the relays A, B. If the wanted subscriber is the called party, his test lead is earthed over the winding p<0>, so that the relay P<3> is energized and connects the buzzer 55 to the relays A, B. Interruption of local connexion. When the operator receives either of the local connexion signals, she informs the subscribers that a trunk connexion is required, the talking circuit being completed over the arms 25, 26 in their fifth position, and then releases the key 5, thus deenergizing the relay B, which moves the sideswitch into its sixth position, in which it is arrested owing to the relay P<2> not being energized. In this position the wanted line is connected over the arms 25, 26 and contacts 65, 66 to the release battery 67. When the local connexion is released, as described in Specification 2672/12, the relay P<2> is energized over the cutoff relay of the wanted subscriber, and by closing contact 58 moves the side-switch into the seventh or conversation position, in which all the branch circuits of the connector are cut off, the release being controlled by the relay C in the test circuit. Release of trunk connexion. The withdrawal of the calling plug de - energizes the relay C which closes the circuit of the side-switch rclease magnet N, and when the side-switch reaches its normal position, the connector release magnet M is brought into parallel with the magnet N, both circuits being open at the off-normal contact 68 when the connector is released.