Patent GB-190322674-A (GB)
Title: Improvements in and connected with Telephone Systems.
Inventor: HARDEGEN PAUL
Filed: 1903-10-20
Granted: 1904-07-07
Abstract: 22,674. Hardegen, P. Oct. 20. Telephone systems.-Relates to telephone systems in which the instruments are installed at certain main stations, with each of which is associated a certain number of subordinate stations (all in the same building, for example). At each main station is an automatic switching device which enables a subscriber on the line wire, or the operator at the exchange, to call up either the main station or any selected one of the subordinate stations connected therewith, without calling up the others or allowing the conversation to be overheard. In the diagram, H represents a main station. I, II, III subordinate stations, V an exchange, and T a subscriber's station on the line 38, 4, continued from the exchange as 39, 5. A device is provided for restoring the automatic switching device to the normal position after a certain interval of time if a subordinate station is called without response. If the call is responded to, the restoration to the normal position takes place only when the called subscriber at the subordinate station hangs up his receiver. A visible " engaged " signal is shown at all the subordinate stations which have not been called up. If a key C is depressed at the subscriber's station T, which is shown connected through the exchange V with the line 39, 5, a current passes from the battery B through the wire 7, relay R', lines 5, 4, key C, and earth. The contact thus made at 10 closes the circuit of the battery D through wires 9, 11, electromagnets f, F, and wire 14. The electromagnet f serves, by the attraction of its armature, to release for one revolution a shaft U, which takes about two minutes to revolve. During this time, contact (normally made) is broken at s, t and m, n, and contact (normally broken) is made at u, v. The electromagnet F actuates a shaft 17 through ratchet gearing, moving the switch arms 24 successively on to the contact blocks 26, 30 ; 27, 31 ; &c. according to the number of times the key C is depressed. The arm 18 indicates on a scale which station (whether main or subordinate) is connected to line at any time. The rotation of the shaft 17 to put one of the subordinate stations to line involves the closing of contacts (normally broken) at 33, 34 and 35, 36. The switch arms 24 having been moved by manipulation of the key C to connect up the required subordinate station, say I, the subscriber at T rings through the metallic circuit 38, 39, 40, 43, 5, 4, the station I alone being called. The closing of the contact u, v completes the circuit of the battery D through the wires 45, 46, electromagnets Q, R, S, and wires 50, 9, thus displaying " engaged " signals 51, 52, 53, and breaking contact at 54, 55, 56. The " engaged " signal P at the main station is also displayed. During the rotation of the shaft U a subscriber at a subordinate station such as II is unable to energize the switch-controlling magnet F in the ordinary way by depressing his key 57, owing to the breaks in the circuit 88 at 55 and m, n. The breaks at 55 &c. continue as long as the contact 33, 34 (which is in shunt to the contact u, v) remains closed. If there is no response on the part of the subscriber at I, the electromagnet L is energized to release the ratchet-wheel and restore the switch arms 23, 24 to the normal position, as soon as the shaft U has completed its rotation. The circuit of the electromagnet L, in that event, comprises the battery D, contacts 36, 35 and t, s, wire 81, the switch hooks of the stations I, II, III, and the wire 50. If a response has been made, this circuit is open at the switch hook of the called subscriber, and the automatic switch does not return to the normal position until the receiver is replaced on the hook. The return of the automatic switch to the normal position breaks the circuit of the electromagnets Q, R, S at 33, 34 and de-energizes them. When the call is made from a subordinate station, by depressing a key 57, the contact device G is not brought into action, the automatic switch alone being operated. The key d is used for closing the circuit of the battery B through the electromagnet E so as to cut off the subordinate stations when the instrument at the main station is in use.