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Updated: May 22, 2025
Throwing in his rheostat he sent an "O.K" in reply, and waited expectantly, pencil in hand. A moment more and he dropped his pencil in disgust. "Just another bug!" he remarked aloud to the thermometer. "Ought to be poisoned! What a whale of a wave length, though!" For several minutes he listened intently, for the amateur was sending insistently, repeating everything twice as if he meant business.
Pieces of iron wire projecting sufficiently in the interior to establish good contacts with the column of mercury are fastened one millimeter apart to the inner surface of the tube. These iron contacts are connected with the divisions of a rheostat, R, arranged in a tight compartment surrounded with paraffine, near the tube. This rheostat is interposed in the general circuit.
The things needed are an arc-lamp, an impedance coil, or small transformer- coil, a rheostat, and a source of energy. The alternating current is not adapted to reproduce speech, but the ordinary direct current is. Of course, the theory isn't half as simple as the apparatus I have described." He had unscrewed the Osram lamp. The talking ceased immediately.
This done connect the or negative electrode of the A battery with the second post of the variable condenser and connect the + or positive electrode with the free post of the first rheostat, the other post of which connects with the free terminal of the filament of the detector.
Begin by laying the various parts out on a base or a panel with the loose coupled tuning coil on the left hand side, but with the adjustable switch of the secondary coil on the right hand end or in front according to the way it is made. Then place the variable condenser, the rheostat, the crystal detector and the binding posts for the head phones in front of and in a line with each other.
There, in a corner concealed by an old chest of drawers, stood a battery of five storage-cells connected with an instrument that looked very much like a telephone transmitter, a rheostat, and a small transformer coil. "I suppose this is a direct-current lighting circuit," he remarked, thoughtfully regarding his find. "I think I know what this is, all right.
It has the same resistance, namely 5,000 ohms as the one used with the 5 watt tube transmitter, but it is a little larger. It is listed at $1.65. The Oscillation Choke Coil. The choke coil in the power circuit is made of about 260 turns of No. 30 B. & S. cotton covered magnet wire wound on a spool 2-1/4 inches in diameter and 3-1/4 inches long. The Filament Rheostat.
An' they did a poor, cheap job av windin' the armature agin. Ye'll be in hot wather wit' the electric-light system until ye put in a new motor. "The rheostat on the searchlight niver was any good; and she may or may not need a new whistle I dunno.
A Simple Vacuum Tube Receiving Set. For this set you should use: a loose coupled tuning coil, a variable condenser, a vacuum tube detector, an A or storage battery giving 6 volts, a B or dry cell battery giving 22-1/2 volts, a rheostat for varying the storage battery current, and a pair of 2,000-ohm head telephone receivers. The Vacuum Tube Detector. With Two Electrodes.
This done connect the other terminal of the filament to one post of the rheostat, the other post of this to the or negative electrode of the 6 volt A battery and the + or positive electrode of the latter to the other terminal of the filament.
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