Patent GB-190623309-A (GB)
Title: A Combined Intercommunication and Exchange Telephone System.
Inventor: BIRNBAUM ISIDORE BERNARD
Filed: 1906-10-20
Granted: 1907-02-21
Abstract: 23,309. Birnbaum, I. B., [Telephon Fabrik Akt.-Ges. vorm. J. Berliner]. Oct. 20. Telephone systems telephones.-In a combined intercommunication and exchange telephone system, all the exchange calls are received at one station of the intercommunication system, and thence transferred to the required station. All the stations of the intercommunication system can communicate one with another without the help of the exchange. Each station has two lever switches C, D co-operating with the two sets of contact-springs E, F. The arrangement is such that, when the lever C is depressed by the knob A, the lever D is also depressed by the rod b ; and when the lever D is raised by replacing the telephone instrument on the support G, the lever C is also raised ; but, when the lever C is raised by depressing the calling- push H, the lever D is unaffected and remains depressed. The exchange lines are connected to the system through the switch CS. Assuming that the exchange wishes to speak to subscriber I, the bell X at the third or last station is rung by current from the exchange passing from the terminal P<a> at station I, to the wire 1, springs f<1>, f<2>, wire 18, and line 28 to terminal P<b> at station II, through springs f<5>, f<6>, wire 30, and line 31 to the next station, and so on to the terminal P<a> of the last station, springs f<1>, f<2>, wire 33, bell X, wire 34, springs f<6>, s, f wire 35, line 36 to station II, and thence in the same way through station I to the exchange terminal P<b>. The subscriber at station III then pushes the button A, thus depressing the levers C, D and completing a speaking - circuit to the exchange; this circuit extends, as described above, to the terminal P<a> of station III and thence through wire 32, springs f<1>, f<3>, wire 40, springs e<1>, e<2>, wires 3, 5, condenser or polarization cell P, wire 6, secondary of induction coil J, receiver T, wire 8, springs g', g<2>, wire 9, contact h of the magneto, wire 10, springs i<1>, i<2>, wire 11, springs e<5>, e<6>, wire 12, springs f<4>, f<5> to terminal P<b>, and thence through stations II, I to the exchange, as before. The subscriber III learns what subscriber is wanted, inserts the plug Z in the proper socket, and depresses the key H, thus completing the circuit of the battery LB through the bell U of the required station 1. Subscriber I then removes his receiver, and is informed by subscriber III that he is wanted by the exchange. The speaking - circuit between the two stations I, III is as follows :-From the plug of station III, terminal L, springs e<4>, e<5>, wire 11, springs i<2>, i', wire 10, contact h, wire 9, springs g', g<1>, wire 8, receiver T, secondary J, wire 6, condenser P, wires 5, 3, springs e', e<3>, terminal EK, common return line to terminal EK at station I, springs e<3>, e', wires 3, 5, condenser P, wire 6, secondary J, receiver T, springs g', g<2>, contact h, wire 10, springs i<1>, i<2>, wire 11, springs e<5>, e<4>, terminal L, to the plug line Z, and thence to station III. Subscriber I then depresses his button A and completes a talking-circuit with the exchange, similar to that previously established by subscriber III. The depression of the lever D by subscriber I or III closes contacts f<7>, f<8> arranged in circuit with a battery SB and the indicators S at each station, which indicate to all other stations that an exchange connexion bas been made. If a subscriber wishes to call the exchange, he depresses the button A, thus connecting the magnets W to the exchange lines. A modified system is described in which a line-selector replaces the plug connexions, and the lever switches C, D are somewhat different, the lever C being released by the movement of the line-selector instead of by the call-push. The levers C, D are formed with tongues engaging a rocking bar connected by links to the rest for the telephone instruments.