Page:Popular Science Monthly Volume 90.djvu/324

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and the bells to the line 2 ; if the switch is down, the telephone will be connected to the line 2 and the bells to line i .

It is best to have the bells produce a different sound on the instruments so that you may tell by the sound which is ringing. If a small nick is filed in one of the bells it will change the tone. — A. A. Davidson.

��Popular Science Monthly

��An Electric Lamp- Socket Lock Clamp and Seal

EXPENSIVE tungsten globes are apt to be a temptation to the petty thief. The illustration shows a new lock for pre- venting the removal of a globe from its socket. It consists of a clamping-ring that fits over the raised portion of the lower end of the socket and is held with a screw. The screw-head is provided with a three-cornered pro- jection inside of a raised ring for a key to enter in turning the screw. Through the raised portion is a hole for a bit of wire, the kind used for seals, to be inserted. The globe cannot be removed without breaking the seal and using the key.

���A sealed lock-clamp on an electric socket

��A Knob- Control for an Inductively Coupled Tuner

A CONVENIENT arrangement whereby an inductively coupled tuner can be operated by means of a round knob on a

��i r.' s '

���FIG.l

�� ��Manner in which the knob is'attached to the shaft to operate a long slide of a tuner

panel receiving set is shown in the drawing, Fig. I. A double-grooved pulley is repre- sented at A J which is locked on the stud- bolt B. This bolt passes through the sleeve C, which is locked on the panel D.

��The handle E is fastened to the other end of the stud-bolt. The method of operation is shown in Fig. 2. This arrangement allows the use of a coupler which has a long slide.

���FI6.2 The method of operation of the knob- control where the coupler has a long slide

A heavy cord is fastened to the secondary coil and passes over the two pulleys E. Each end of the cord is led to a separate groove in the pulleys A. The cord can be fastened on the pulley by drilling small holes in the flange of A and tying knots securely in it. The size of pulley A is determined by the length of the slide of the loose coupler. — D. R. Simmons.

Remover for Insulation on Electric Wires

TO remove, or skin the insulation from a wire, cut a V-shaped slot having curved sides in the end of a flat bar of tool steel, as shown in the detail. For practical purposes a bar of steel 3 in. long, 1 3^ in. wide and 3^ in. thick will be needed. Two holes are drilled below the apex of the slot for screw- ing the cutter to the workbench. When an insulated wire is pressed into the slot, the sharp edges cut through to the wire and its covering is readily removed by a

quick pull downward. Removing the in- — E. B. Williams. sulation from wires

���How to Make a Portable Aerial for Wireless

A COM PACT aerial that can be carried in the pocket may be improvised from a long steel tape measure, such as is used by surveyors or building contractors. When not in use it can be rolled up into its case and carried in the pocket. Although steel does not have the conductivity of copper, such a tape has given very good results, when strung from a tree or housetop to the receiving set. Arlington has been heard clearly in New York when this kind of an aerial was employed.

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