-<P>All filters work in basically the same way. There are several elements delimited by commas.
-There can be many lines in the filter and they are read from the top by the program.
-When writing a filter you need to think carefully about just what you want to achieve. You
-are either going to write a filter to <EM>accept</EM> or to <EM>reject</EM>.
-Think of a filter as having 2 main elements. For a reject filter, you would have a line
-or multiple lines rejecting the things you do not wish to receive and then a default
-line accepting everything else that is not included in the filter. Likewise, for an
-accept filter, you would have a line or multiple lines accepting the things you wish
-to receive and a default line rejecting everthing else.
-<P>
-<P>In the example below, a user requires a filter that would only return SSB spots
-posted in Europe on the HF bands. This is achieved by first rejecting the CW section
-of each HF band and rejecting all of VHF, UHF etc based on frequency.
-Secondly, a filter rule is set based on CQ zones to only accept spots posted in
-Europe. Lastly, a default filter rule is set to reject anything outside the filter.
-<P>
-<BLOCKQUOTE><CODE>
-<PRE>
-$in = [
- [ 0, 0, 'r', # reject all CW spots
- [
- 1800.0, 1850.0,
- 3500.0, 3600.0,
- 7000.0, 7040.0,
- 14000.0, 14100.0,
- 18068.0, 18110.0,
- 21000.0, 21150.0,
- 24890.0, 24930.0,
- 28000.0, 28180.0,
- 30000.0, 49000000000.0,
- ] ,1 ],
- [ 1, 11, 'n', [ 14, 15, 16, 20, 33, ], 15 ], #accept EU
- [ 0, 0, 'd', 0, 1 ], # 1 = want, 'd' = everything else
-];
-</PRE>
-</CODE></BLOCKQUOTE>
-<P>
-<P>The actual elements of each filter are described more fully in the following sections.
-<P>
-<H2><A NAME="ss5.1">5.1 Spots</A>