00100		It will be necessary to know a little about elementary electronics,
00200	and, to that end, we will briefly look at some Physics.  All matter is 
00300	composed of atoms. For our purposes, it will be adequate to consider atoms
00400	to be very small round objects, composed of a nucleus, surrounded by electrons.
00500	The number and arrangement of the electrons around the nucleus is determined
00600	by (determins?) the particular type of matter that the atom is an atom of.
00700	Some substances, called elements, are composed of only one type of atom.
00800	Other substances, called compounds, are composed of combinations of different
00900	types of atoms -- they are combinations of elements.
01000		The electrons of an atom are more or less free to move from one
01100	atom to the next.  This movement of electrons is electricity.
01200		Some atoms hold on to their electrons more firmly that others, and,
01300	therefor, some matterials allow electric current to flow more easily than
01400	others.  Substances which allow this flow to happen easily are called
01500	conductors; substances which do not allow this are called insulators.
01600	In general, metals are good conductors, and things like rubber, plastics,
01700	cloth, etc. are insulators.
01800		Two important electrical quantities are voltage and current.
01900	If there are two pieces of metal which are not connected together, and
02000	if one of them has significantly more electrons than the other, then
02100	there is a voltage between the two pieces of metal.  Voltage is always
02200	measured between two points and indicates that one of the points has
02300	relatively more electrons than the other -- voltage indicates that
02400	electrons would like to flow from one point to another.  If the two
02500	pieces of metal which have a non-zero voltage between them are connected
02600	together by a wire, then electrons will flow from the one with more
02700	electrons, to the one with fewer electrons, until the voltage becomes
02800	zero.  This movement of electrons is current.  Current is always measured
02900	at one point, and it indicates the number of electrons flowing past
03000	that point.