one of the several hundred thousand persons in the United States who
are interested in wireless telegraphy and telephony; _second_, that
you would like to install an apparatus in your home, and _third_, that
it is all new to you.

Now if you live in a city or town large enough to support an
electrical supply store, there you will find the necessary apparatus
on sale, and someone who can tell you what you want to know about it
and how it works. If you live away from the marts and hives of
industry you can send to various makers of wireless apparatus
[Footnote: A list of makers of wireless apparatus will be found in the
_Appendix_.] for their catalogues and price-lists and these will give
you much useful information. But in either case it is the better plan
for you to know before you start in to buy an outfit exactly what
apparatus you need to produce the result you have in mind, and this
you can gain in easy steps by reading this book.

Kinds of Wireless Systems.--There are two distinct kinds of wireless
systems and these are: the _wireless telegraph_ system, and the
_wireless telephone_ system. The difference between the wireless
telegraph and the wireless telephone is that the former transmits
messages by means of a _telegraph key_, and the latter transmits
conversation and music by means of a _microphone transmitter_. In
other words, the same difference exists between them in this respect
as between the Morse telegraph and the Bell telephone.

Parts of a Wireless System.--Every complete wireless station, whether
telegraph or telephone, consists of three chief separate and distinct
parts and these are: (a) the _aerial wire system_, or _antenna_ as it
is often called, (b) the _transmitter_, or _sender_, and (c) the