How to Mount the Parts.--Now mount the coil on a wood base, 1/2 or 1 inch thick, 3-1/2 inches wide and 5-1/2 inches long, and then connect one end of the coil to one of the end points on the switch, and connect each succeeding tap to one of the switch points, as shown schematically in Fig. 99 and diagrammatically in Fig. 100. This done, screw the switch down to the base. Finally screw the detector to the base and screw two binding posts in front of the coil. These are for the earphone.

[Ill.u.s.tration: Fig. 99.--Schematic Layout of $5.00 Receiving Set.]

[Ill.u.s.tration: Fig. 100.--Wiring Diagram for $5.00 Receiving Set.]

The Condenser.--You do not have to connect a condenser across the earphone but if you do you will improve the receiving qualities of the receptor.

How to Connect Up the Receptor.--Now connect up all the parts as shown in Figs. 99 and 100, then connect the leading-in wire of the aerial with the lever of the switch; and connect the free end of the tuning coil with the _ground_. If you have no aerial wire try hooking it up to a rain pipe that is _not grounded_ or the steel frame of an umbrella. For a _ground_ you can use a water pipe, an iron pipe driven into the ground, or a hydrant. Put on your headphone, adjust the detector and move the lever over the switch contacts until it is in adjustment and then, if all your connections are properly made, you should be able to pick up messages.

[Ill.u.s.tration: Wireless Set made into a Ring, designed by Alfred G.

Rinehart, of Elizabeth, New Jersey. This little Receptor is a Practical Set; it will receive Messages, Concerts, etc., Measures 1"

by 5/8" by 7/8". An ordinary Umbrella is used as an Aerial.]

APPENDIX

USEFUL INFORMATION

ABBREVIATIONS OF UNITS

Unit Abbreviation

ampere amp.

ampere-hours amp.-hr.

centimeter cm.

centimeter-gram-second c.g.s.

cubic centimeters cm.^3 cubic inches cu. in.

cycles per second ~ degrees Centigrade C.

degrees Fahrenheit F.

feet ft.

foot-pounds ft.-lb.

grams g.

henries h.

inches in.

kilograms kg.

kilometers km.

kilowatts kw.

kilowatt-hours kw.-hr.

kilovolt-amperes kv.-a.

meters m.

microfarads [Greek: mu]f.

micromicrofarads [Greek: mu mu]f.

millihenries mh.

millimeters mm.

pounds lb.

seconds sec.

square centimeters cm.^2 square inches sq. in.

volts v.

watts w.

PREFIXES USED WITH METRIC SYSTEM UNITS

Prefix Abbreviation Meaning

micro [Greek: mu]. 1 millionth milli m. 1 thousandth centi c. 1 hundredth deci d. 1 tenth deka dk. 10 hekto h. 1 hundred kilo k. 1 thousand mega m. 1 million

SYMBOLS USED FOR VARIOUS QUANt.i.tIES

Quant.i.ty Symbol

capacitance C

conductance g

coupling co-efficient k

current, instantaneous i

current, effective value I

decrement [Greek: delta]

dielectric constant [Greek: alpha]

electric field intensity [Greek: epsilon]

electromotive force, instantaneous value E

electromotive force, effective value F

energy W

force F

frequency f

frequency x 2[Greek: pi] [Greek: omega]

impedance Z

inductance, self L