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. 



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. 



