Aerial Switch for a Complete Sending and Receiving Set.--You can buy a double-pole, double-throw switch mounted on a porcelain base for about 75 cents and this will serve for Set No. 1. Screw this switch on your table between the sending and receiving sets and then connect one of the middle posts of it with the ground wire and the other middle post with the lightning switch which connects with the aerial. Connect the post of the tuning coil with one of the end posts of the switch and the clip of the tuning coil with the other and complementary post of the switch. This done, connect one of the opposite end posts of the switch to the post of the receiving tuning coil and connect the sliding contact of the latter with the other and complementary post of the switch as shown in Fig. 26.

Connecting in the Lightning Switch.--The aerial wire connects with the middle post of the lightning switch, while one of the end posts lead to one of the middle posts of the aerial switch. The other end post of the lightning switch leads to a separate ground outside the building, as the wiring diagrams Figs. 26 and 27 show.

[CHAPTER V]

ELECTRICITY SIMPLY EXPLAINED

It is easy to understand how electricity behaves and what it does if you get the right idea of it at the start. In the first place, if you will think of electricity as being a fluid like water its fundamental actions will be greatly simplified. Both water and electricity may be at rest or in motion. When at rest, under certain conditions, either one will develop pressure, and this pressure when released will cause them to flow through their respective conductors and thus produce a current.

Electricity at Rest and in Motion.--Any wire or a conductor of any kind can be charged with electricity, but a Leyden jar, or other condenser, is generally used to hold an electric charge because it has a much larger capacitance, as its capacity is called, than a wire. As a simple analogue of a condenser, suppose you have a tank of water raised above a second tank and that these are connected together by means of a pipe with a valve in it, as shown at A in Fig. 28.

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original © Underwood and Underwood.
First Wireless College in the World, at Tufts College, Mass.