Patent GB-190526348-A (GB)
Title: Improvements in and relating to Systems of Connections for the Operation of Branch Telephone Stations and the like.
Inventor: OHNESORGE WILHELM
Filed: 1905-12-18
Granted: 1906-06-14
Abstract: 26,348. Ohnesorge, W. Dec. 17, 1904, [date applied for under Patents Act, 1901]. Telephone systems.-Relates to means for supplying current to branch stations in central-battery exchange systems in such a manner that two branch stations may speak together without interrupting a conversation proceeding between the exchange and the main station from which they branch. In the arrangement shown in Fig. 1, the stations A, B are connected through the exchange C. Connected with the main station B are four branch stations E, F, G, H. The microphone current of station A flows through the inductance coils 7, 8 to the line-wires 13, 14 in parallel, and thence through the resistances 17, 18 to earth at 20. Current is supplied similarly to the microphone 53 at station B and flows thence through the line 21 to the inductance coils 23, 24, where it divides between the stations E, F, returning by the lines 41, 42 and earth. The receiving-instruments 10,9, 49, 50 are arranged so as to bridge the double line at the main and branch stations. Owing to this bridge arrangement, the current fluctuations in the transmitter 53 fail to affect the receivers 49, 50, and the current fluctuations in the transmitters 45, 46 fail to affect the receiver 9. A plug or similar switchboard P is provided at the main station B for making connexions between the branch stations. A condenser or polarization cell 40 is arranged as shown in Fig. 1 to prevent currents induced in the single wire 21 from reaching the speaking-instruments at the main station B. Additional single feed-wires may branch off from the point 19. The receiver 9 may be bridged across the line in front of instead of behind the transmitter 53, as indicated by dotted lines. Instead of taking off the branch 21 from the point 19, that point may be earthed, and the branch taken off through inductance coils from the two line-wires 11, 12 between the exchange and the main station B. Several branches may be taken off, each through its own pair of coils. At the branch stations, the coils 32, 33 may be connected directly to earth, the third wires 41, 42 being dispensed with. In a further modification, the central battery which supplies current to the stations A, B bridges the cord circuit in the usual way, an extra battery being connected between one of its terminals and earth for the purpose of supplying current to the branch stations. In another modification, shown in Fig. 4, the central battery is arranged bridge-wise with respect to the line 13, 14, but is connected in the manner shown in Fig. 1 with respect to the line 11, 12 leading to the main station B to which the branch stations E, F are connected. The coils 5, 6, 7, 8 may be the windings of relays for calling and clearing purposes &c. Arrangements may be made at the board P for enabling the branch stations to speak with the exchange. The coils 15, 16, &c. are formed as opposing coils on a common iron core in order to avoid damping of the fluctuations of the microphone current.