Patent GB-190910203-A (GB)
Title: Improvements relating to Service Registers in Telephone Installations.
IPC: H04M15/10
Filed: 1909-04-29
Granted: 1909-09-09
Abstract: 10,203. Siemens Bros. & Co., [Siemens & Halske Akt.-Ges.]. April 29. Exchange systems; metering systems.-Relates to the operation of service registers in telephone systems in which the circuit of the ring-off signal is closed over the third lead of the cord-circuit and the socket-lead, and in which the register electromagnet is brought into a local circuit on the insertion of the answering-plug, the registration being effected over the third lead of the cordcircuit. The register electro-magnet Z has two oppositely-wound windings w<1>, w<2> so calculated that during conversation and when the receivers are hung up, the register is not affected. The invention is generally applicable but is especially suitable for systems in which the calling-relay controls the ring-off signal as described later. When the subscriber T' calls, the calling-relay AR<1> completes a circuit through the winding r<2> of the auxiliary relay HR<1>, which closes the circuit of the call lamp AL<1>. The insertion of the enquiry plug AS closes the contact k and completes a circuit from the battery B through the ring-off lamp SL and winding w<1> in parallel, winding w<2>, contact k, and winding r<1> to ground and back to the battery. The windings w<1>, w<2> neutralize each other so that the register is not actuated at this point. The current through the winding r<1> also neutralizes the effect of the winding r<2> so that the call lamp AL<1> is extinguished. The resistance of the winding w<1> prevents the ring-off lamp SL from glowing, but when the call relay is de-energized at the termination of a conversation its armature falls back and short-circuits the winding r<1>, the consequent increase in current causing the lamp SL to glow. Registration is effected by depressing the key T either before or after the ring-off signal is given. The depression of the key T cuts out the lamp SL from its parallel connexion with the winding w<1> and at the same time puts the low-resistance relay n in parallel with the winding w<2>, thereby increasing the current in the winding w<1> and decreasing that in the winding w<3>. The register is thus actuated and its armature z short-circuits the winding w<2>, at the same time completing a holding- on circuit for the winding w<1>, and also opening at q a short-circuit round a resistance p so that, when the key T is released, this resistance is put in the circuit of the lamp SL so that the same current flows through this lamp as before registration. A control relay n<1> is connected between the armature of the relay n and a resistance x connected to the battery B through the lower contact of the key T. Until the register has actuated, the drop in potential in the currents through the relay n and the resistance x is such that the relay n<1> is not energized, but when the resistance p is introduced into the socket-lead the balanceof potential is disturbed, causing the relay n<1> to complete the circuit of the control lamp CL. In order that the ring-off lamp UL and winding r<3> of the auxiliary relay of the called subsoriber may receive the same currents as the lamp SL and winding r<1> respectively, the lamp UL is shunted by a resistance o equal to the resistance of the winding w<1>, and a resistance m equal to the resistance of the winding w<2> is inserted in the third lead of the connecting-plug or in the socket lead as shown in dotted lines.