+<P>There are two main types of filter, <EM>accept</EM> or <EM>reject</EM>. You
+can use either to achieve the result you want dependent on your own preference
+and which is more simple to do. It is pointless writing 8 lines of reject
+filters when 1 accept filter would do the same thing! Each filter has 10
+lines (of any length) which are tried in order. If a line matches then the
+action you have specified is taken (ie reject means ignore it and accept
+means take it)
+<P>
+<P>If you specify reject filters, then any lines that arrive that match the filter
+will be dumped but all else will be accepted. If you use an accept filter,
+then ONLY the lines in the filter will be accepted and all else will be dumped.
+For example if you have a single line <EM>accept</EM> filter ...
+<P>
+<BLOCKQUOTE><CODE>
+<PRE>
+accept/spots on vhf and (by_zone 14,15,16 or call_zone 14,15,16)
+</PRE>
+</CODE></BLOCKQUOTE>
+<P>then you will <EM>ONLY</EM> get VHF spots <EM>from</EM> or <EM>to</EM> CQ zones
+14, 15 and 16.
+<P>
+<P>If you set a reject filter like this ...
+<P>
+<BLOCKQUOTE><CODE>
+<PRE>
+reject/spots on hf/cw
+</PRE>
+</CODE></BLOCKQUOTE>
+<P>Then you will get everything <EM>EXCEPT</EM> HF CW spots. You could make this
+single filter even more flexible. For example, if you are interested in IOTA
+and will work it even on CW even though normally you are not interested in
+CW, then you could say ...
+<P>
+<BLOCKQUOTE><CODE>
+<PRE>
+reject/spots on hf/cw and not info iota
+</PRE>
+</CODE></BLOCKQUOTE>
+<P>But in that case you might only be interested in iota and say:-
+<P>
+<BLOCKQUOTE><CODE>
+<PRE>
+accept/spots not on hf/cw or info iota
+</PRE>
+</CODE></BLOCKQUOTE>
+<P>which achieves exactly the same thing. You should choose one or the other
+until you are comfortable with the way it works. You can mix them if you
+wish (actually you can have an accept AND a reject on the same line) but
+don't attempt this until you are sure you know what you are doing!
+<P>
+<P>You can arrange your filter lines into logical units, either for your own
+understanding or simply convenience. Here is an example ...
+<P>
+<BLOCKQUOTE><CODE>
+<PRE>
+reject/spots 1 on hf/cw
+reject/spots 2 on 50000/1400000 not (by_zone 14,15,16 or call_zone 14,15,16)
+</PRE>
+</CODE></BLOCKQUOTE>
+<P>What this does is to ignore all HF CW spots and also rejects any spots on VHF
+which don't either originate or spot someone in Europe.
+<P>
+<P>This is an example where you would use a line number (1 and 2 in this case), if
+you leave the digit out, the system assumes '1'. Digits '0'-'9' are available.
+This make it easier to see just what filters you have set. It also makes it
+more simple to remove individual filters, during a contest for example.
+<P>
+<P>You will notice in the above example that the second line has brackets. Look
+at the line logically. You can see there are 2 separate sections to it. We
+are saying reject spots that are VHF or above <EM>APART</EM> from those in
+zones 14, 15 and 16 (either spotted there or originated there). If you did
+not have the brackets to separate the 2 sections, then Spider would read it
+logically from the front and see a different expression entirely ...
+<P>
+<BLOCKQUOTE><CODE>
+<PRE>
+(on 50000/1400000 and by_zone 14,15,16) or call_zone 14,15,16
+</PRE>
+</CODE></BLOCKQUOTE>
+<P>The simple way to remember this is, if you use OR - use brackets. Whilst we are
+here CASE is not important. 'And BY_Zone' is just the same as 'and by_zone'.
+<P>As mentioned earlier, setting several filters can be more flexible than
+simply setting one complex one. Doing it in this way means that if you want
+to alter your filter you can just redefine or remove one or more lines of it or
+one line. For example ...
+<P>
+<BLOCKQUOTE><CODE>
+<PRE>
+reject/spots 1 on hf/ssb
+</PRE>
+</CODE></BLOCKQUOTE>
+<P>would redefine our earlier example, or
+<P>
+<BLOCKQUOTE><CODE>
+<PRE>
+clear/spots 1