Page:Popular Science Monthly Volume 90.djvu/174

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158

��Popular Science Monthly

��will be wedge-shaped, 5/16 in. deep at the top and 1/16 in. deep at the bottom. It is essential that the cut be exactly 5/16 in. deep at the topy and it might be well to use some sort of a guide for the sake of ac- curacy. In Fig. 3 is illustrated the proper way to make these slits.

With a small drill make 10 holes diag- onally through the cover at the same spac- ing as that of the slots in the tube, so that the drill enters at 1 3^ in. from the top edge and emerges 3^ in. from the bottom edge. If a No. 24 drill cannot be obtained make one of steel wire. Make 10 springs from the brass wire by twisting it around a nail and cutting to the proper lengths. The dimensions of these springs are shown in Fig. 2. Insert the springs in the holes in the cover. Then nail or glue the wood tubes to the cover so that the springs slide in the slots. File one end of the brass rod to a point, fit the insulating knob on the other and slide the rod into the tube. This rod should slide easily and make connection with all of the springs.

After connecting the alternate condenser- plates together make a tinfoil-lead to the first spring. Twist the tinfoil to the end of the spring beneath the cover and solder it on by heating gently. By "first spring" is meant the spring 2 in. from the end of the tube. Each half of the condenser-plates remaining should be similarly connected with the other springs. Complete the con- denser by pouring melted wax into the case, and attach the cover. If this condenser is to be used in a cabinet set, a hole can be rtiade in the cabinet-front through which the rod may be pulled either way. If a scale is desired on the cabinet-front it will necessitate a change in the position of the condenser and the working of the rod by means of levers. — Harry Rattner.

��A Quick Method of Removing Enamel from Magnet-Wire

MANY operators prefer enameled wire on tuning coils and couplers but the wire is apt to break when winding coils with the finer wire. To scrape the wire for removing the enamel causes it to break. About the only way to remove the enamel quickly is to pass it through the flame of a bunsen or alcohol burner, which will melt the coating until it runs off. A much slower way is to soak the wire in alcohol until it dissolves the enamel, which is the best method for the smaller wires where they must be measured accurately.

��An Easily Learned Emergency Telegraph Code

A TELEGRAPH code which can be learned in a few minutes and which is composed entirely of dots has great possi- bilities for use in an emergency.

To learn the system it is only necessary to write down the alphabet in its usual order, placing six letters to a line. A to F, inclusive, will constitute the first line; G to L, inclusive, the second line; and so on. The fifth line will be composed of Y and Z only, as shown. Punctuation marks may be assigned to the remaining spaces.

�� �1

�2 3

�4

�5

�6

�1

�A

�B C

�D

�E

�F

�2

�G

�H I

�J

�K

�L

�3

�xM

�N

�P

�Q

�R

�4

�S

�T U

�V

�vv

�X

�5

�Y

�Z

�?

�/

��Table for learning the dots nec- essary to send a letter signal

The dots for each letter are ascertained by numbering each with two numerals; first a numeral indicating the group to which the letter belongs and second its position in that group. Thus A is i-i, B is 1-2, C is 1-3, and so on, to F, 1-6. The second group is numbered similarly from one to six except that the number in- dicating the group is 2 instead of i. The second letter in the fifth group, Z, is 5-2.

After a person has written out the alpha- bet in this manner and set it before him, he can with very little practice spell out any message he may desire to send. For ex- ample, the word "radio" would be: 3 dots, short pause, 6 dots (R), longer pause; I dot, pause, i dot (A), longer pause; i dot, pause, 4 dots (D), longer pause; 2 dots, pause, 3 dots (I), longer pause; 3 dots, pause, 3 dots (O).

Amateur wireless operators, boy scouts, miners in distress, mariners, ignorant of the Morse code will find this simple code useful.

For sending numerals, the 10 digits are expressed by dots corresponding to their value, naught being indicated by 3-3.

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