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Updated: May 22, 2025
Connect the first post of the variable condenser to the + or positive electrode of the A battery and its or negative electrode with the rotating contact arm of the rheostat. Next connect one end of the resistance coil of the rheostat to one of the posts of the amplifier tube that leads to the filament and the other filament post to the + or positive electrode of the A battery.
Despite the fact that the voltmeter seemed to be shorted out by the relux plate, the needle pointed steadily at twenty-two. Arcot changed the current through the magnet, and the reading dropped to twenty. The rays had been on at very low power, the air only slightly ionized, but as Arcot turned a rheostat, the intensity increased, and the air in the path of the beam shone with an intense blue.
Connect the lead that runs from the second post of variable condenser to the first post of the third rheostat, the second post of which is connected with one terminal of the second amplifying tube; then connect the first post of the rheostat with one end of the secondary coil of the second audio frequency transformer and the other end of this coil with the grid of the second amplifier tube.
In measure as the level of the water rises, the pressure on the mercury in the receptacle increases, and causes the metal to rise in the tube. The higher the level of the sea, the less becomes the sum of the resistances of the rheostat, since the column of mercury puts in short circuit all the divisions of the rheostat, whose contacts are comprised in the height of the column.
Set the vacuum tube amplifier back of the rheostat and the A and B batteries back of the parts or in any other place that may be convenient. The fixed condensers and the grid leak can be placed anywhere so that it will be easy to connect them in and you are ready to wire up the set. Connecting Up the Parts for a Crystal Detector.
In the same way carbon, whether solid or in the shape of finely divided powder, offers a high resistance to the passage of electricity; but if the carbon is squeezed together the conditions change, with less resistance to electricity in the circuit. For his quadruplex system, Mr. Edison utilized this fact in the construction of a rheostat or resistance box.
A rheostat of this kind is shown at I and is listed at $1.25. The Oscillation Choke Coil. This coil is connected in between the oscillation circuits and the source of current which feeds the oscillator tube to keep the oscillations set up by the latter from surging back into the service wires where they would break down the insulation.
To do this you need only to use a voltmeter across the filament terminals instead of an ammeter in series with it; then regulate the voltage of the filament with a rheostat. The Operation of C. W. Telegraph Transmitters with Alternating Current With Two Oscillator Tubes. In other words these oscillations are sustained but as in the case of those of a single tube, their amplitude rises and falls.
A rheostat is also useful in that it keeps the filament from burning out when the current from the battery first flows through it. You can very often increase the sensitiveness of a vacuum tube after you have used it for a while by recharging the A or storage battery. The degree to which a vacuum tube has been exhausted has a very pronounced effect on its sensitivity.
The tube costs $8.00 and the porcelain base is $1.00 extra. It is shown at E. The Storage Battery and Rheostat. This must be a 5-cell battery so that it will develop 10 volts. A storage battery of any capacity can be used but the lowest priced one costs about $22.00. The rheostat for regulating the battery current is the same as that used in the preceding experimental transmitter.
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