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Page:Popular Science Monthly Volume 89.djvu/636

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622

��Popular Science Monthly

��Tapping Field Telephone Wires with a Pocket Connector

THE device illustrated is used in field work for tapping telephone wires where it is necessary to make a call on the line at any point. It is made from the body of the arms that form the ordinary machinist's divider. The sharp, tapering points are cut from a 9-in. tool, leaving square stubs 5 in. long. In the ordinary divider the arms are set apart to allow space for the spring. The arms must be bent to take up the space so that their inner surfaces come close together, then holes are drilled with their centers on the parting surfaces so that one-half the hole is in each member. Two of those holes are shown having different sizes to admit wires of different diameters. Small holes are drilled at right angles to these holes to intersect the half- hole in one arm and steel phonograjjh needles are inserted in them.

Another small hole is drilled through one arm anil intersected at right angles with another, which is tapped to receive a knurled head machine screw. This is used for attaching a con- necting wire to the receiver of the tele- phone.

���In ordinary use the connector is held on the wire by hand, but if connections are wanted for any length of time it is best to retain the wing with its nut and screw. In this case the wing should be cut off, allowing only a ^^-in. stub to project. The device is opened wide enough to clear the stub of the wing to admit the wire, then it is closed and the wing-nut set. The needles should not project too far or they will se\er the wire.

���A new type vacuum tube relay

��A small iH>ckct device for mnkin); conncc- liuns anywhere on a field telephone line

��Strengthening the Static Field of an Amplifier

THIi so-called audion principle, es- pecially when used in telephone relays, has been applied to \acuum tubes built in a great \'ariety of ways.

\\'hen the grid, or corresponding electrode through which energy to be amplified is led to the device, is placed close to the filament, the local battery cur- rent is usually controlled most efficiently. The closer t he grid and the filament are lirought together, (he stronger will be the static field between them, and the better the amplification. It is necessary, however, to keep the two out of actual electrical contact. If current could How directly from the grid to (he filament the relay would be partially short-circuited and consequent- ly would not work.

U. S. patent 1,169,422, issued in I9i(> to A. M. Nicholson, shows the type of vacuum tube relay illustrated. The U- shaped electrode 1 is that through which the incoming feeble cmreiits produce their efTects, and takes tlu' place of the grid in the more usual form <if tube. The lilanient 2 is entwined about the U- ilcclrode I, being wound aclually upon it. The two are kept a])art by the insu- lating effects of a thin la>'er of nickel t).\ide on the forked conductor. The plates 3, 3 are connected with the local ballcry, and the whole relay structure is enclosed in the evacuated bulb 4.

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