GB190711823A - Improvements in Devices for Amplifying Variable Electrical Currents of Telephonic or like Character. - Google Patents

Abstract

11,823. Lake, H. W., [Stone, J. S.]. May 21. Telephone systems; telephones; phonographs &c. -Relates to apparatus for increasing the intensity or amplitude of varying electric currents such as are employed in telephonic transmission, and is particularly described with reference to the amplification of currents induced in the solenoid of an electro-magnet A by a moving telephonic record C, thus increasing the amplitude of the sound waves produced by the reproducing telephone T. The solenoid of the electro-magnet A is connected in series with two solenoids 6 wound on the pole-pieces of the permanent magnet 6<1>. Any variation in the current flowing in the solenoids 6 causes a variation in the force with which the armature 7 is attracted by the magnet 6<1>. This armature is rigidly connected to the insulated diaphragm 8, to the vibrating electrode of the microphone, and to the light frame 17, which in turn is fixed to a stretched wire 20 which supplies the restraining force to the pull of the magnet 6<1> on the armature 7. The diaphragm 8 is attached to the metallic frame 2 by means of springs 10. The box 15, which is rigidly attached to the frame 16, contains the fixed electrode of the microphone and the carbon granules. The vibrating electrode is attached to this box by means of a mica diaphragm. The battery current enters at the binding-post d and passes through the wire x to the vibrating electrode, and by means of the carbon granules to the fixed electrode, and thence through the frame and wire y to the primary I<1> of a step-up induction coil and back to the battery B. The reproducing telephone T is connected to the terminals of the secondary coil I<2> of the induction coil. To reduce friction, the whole apparatus may be enclosed in a bell jar 25 from which the air may be exhausted.