A '''filter''' is any [[oscillator]] used to delete some but not all of the [[spaceship]]s in a stream. An example is the [[blocker]], which can be positioned so as to delete every second [[glider]] in a stream of period 8n+4, and can also do the same for [[LWSS]] streams. Other examples are the [[MW emulator]] and [[T-nosed p4]] (either of which can be used to delete every second LWSS in a stream of period 4n+2), the [[fountain]] (which does the same for MWSS streams) and a number of others, such as the [[pipsquirter 1|p6 pipsquirter]], the [[pentadecathlon]] and the [[two blockers hassling R-pentomino]] oscillator shown under {{LinkLexicon|style=raw|filename=lex_f.htm#factory|patternname=factory}}.
A '''filter''' is an [[oscillator]] used to delete some but not all of the [[spaceship]]s in a [[stream]]. For example, a [[blocker]] can delete every second [[glider]] in a stream of [[period]] 8n+4, and can also do the same for [[LWSS]] streams. Other examples are the [[middleweight emulator]], [[T-nosed p4]] (either of which can be used to delete every second LWSS in a stream of period 4n+2) and the [[fountain]] (which does the same for MWSS streams).
Filters can be used to make guns of very high periods without crossing two guns, for example, the [[period-20 glider gun]] can be made p40 by adding a [[blocker]], then p80 by adding [[Rich's p16]], and even p160 by adding [[68P32.1]]:
Filters can be used to make guns of high periods. For instance, the [[period-20 glider gun]] can be made p40 with a blocker, then p80 with [[Rich's p16]], and even p160 with [[68P32.1]]:
A filter is an oscillator used to delete some but not all of the spaceships in a stream. For example, a blocker can delete every second glider in a stream of period 8n+4, and can also do the same for LWSS streams. Other examples are the middleweight emulator, T-nosed p4 (either of which can be used to delete every second LWSS in a stream of period 4n+2) and the fountain (which does the same for MWSS streams).
Filters can be used to make guns of high periods. For instance, the period-20 glider gun can be made p40 with a blocker, then p80 with Rich's p16, and even p160 with 68P32.1: