THE WORLD'S ADVANCE 



251 



ever, the hinging is suggested as it not 

 only affords accessibility, but also sim- 

 plifies the connecting of the instruments. 



Fasten the first primary to the bot- 

 tom of the box or the top as the case 

 may be by means of small tacks, or a 

 thin brass strip. Support the second by 

 thin brass clips as illustrated in Fig. n. 

 The couplers must be mounted as illus- 

 trated with their planes at right angles 

 to each other, in order that no mutual 

 inductance may exist between them. 



Slip a 3/1 6" rod 16" long, threaded 

 10-24 f r I2 " of its length, through the 

 primaries and secondaries as indicated, 

 fastening the secondaries in position 

 with lock nuts at right angles to each 

 other. One end of the box serves as 

 one support and bearing for this rod. At 

 the other any convenient form of sup- 

 port may be arranged. The handle 

 should be graduated for one-quarter of 

 its circumference into eight equal divi- 

 sions in order that the coupling may be 

 readily set to any degree. It is unneces- 

 sary to move the secondaries through a 

 greater angle than 90, and if this is ex- 

 ceeded, connections are liable to be dis- 

 turbed. 



Fasten the loading coil to the con- 



'- 



fued condenser <* Conto/ner 



The Case of the Fixed Condenser. 



tainer box with two brass strips, or by 

 turning up wooden standards for it. 



Before mounting the switches, make 

 a full-sized drawing of the top and sides 

 on paper, laying out the positions of con- 

 tact points and switch centers on the pa- 

 per. Then place the paper on the box, 

 and indicate all holes by light punch 

 marks through the paper. This prevents 

 unnecessary scarring-up of the box. 



The circles indicated for the switches 

 are the circles on which the contact cen- 

 ters are placed. The contacts are 1/4" 

 apart, measuring from center to center, 

 and are placed as indicated in the con- 

 nection diagram. The A switches have 



hferior Loyovf 

 f/gJJ 



Arrangement of Loose Couplers and Loading Coll. 



four points per side, while type B is an 

 eight-point switch with its contacts 

 spaced l / 2 " apart, center to center. The 

 telephone switch, if used should be 

 placed between the B and C switches. 



No attempt has been made to describe 

 the construction of the three variable 

 condensers, which should be of the ro- 

 tary plate type. Should the reader desire 

 to make them, he is referred to an ex- 

 cellent description in Electrician and 

 Mechanic for October, 1912, or the plates 

 may be purchased from the makers of 

 variable condensers. Condensers Nos. i 

 and 2 should be filled with castor oil to 

 the level of the top plates. The conden- 

 ser in the detector circuit is kept at the 

 original capacity. The condenser in the 

 intermediate circuit should have a thin 

 copper strip fastened to the stationary 

 plates so that the condenser is short- 

 circuited when turned past zero. 



The small fixed condenser consists of 

 eight strips of foil, measuring 6" x i", 

 placed between paraffined paper meas- 

 uring 6" x iy 2 " '; the foil projecting at 

 opposite ends. It should be rolled up 

 and slipped wi-thin the tube prepared for 

 it, the terminal being connected to the 

 binding posts which slip on studs pro- 

 jecting from the box. (See Fig. 10.) O 

 is in the audion box. 



While connecting wires may be strung 



