Bistable switch

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Bistable switch
x = 75, y = 61, rule = B3/S23 2bo$obo$b2o11$50bo$50b3o$53bo$52b2o2$45b2o17b2o$46bo17bo$46bobo13bobo$ 47b2o13b2o3$44bo$42bobo$43b2o10bo$54bobo$54bobo$55bo12$73b2o$73b2o4$ 61bo$60bobo$61b2o9$49b2o$48bobo$48bo$47b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]]
Pattern type Memory cell
Number of cells 43
Bounding box 30×48
Discovered by Paul Callahan
Year of discovery 1994

The bistable switch is a partial stable reflector discovered in 1994 by Paul Callahan.


The switch consists of elementary still lifes. More specifically, it uses a block and eater 1, together with a century eater consisting of three eater 1s surrounding a central beehive. In addition to these permanent catalysts, there is an extra still-life to represent the state. This can either be a block or boat, depending on the state.

Reflecting ability

The switch was found when trying to build a stable reflector. When the glider collides with the boat, it is converted into a block and a glider is emitted perpendicular to the incident glider. When a glider (on a different path) collides with the block, it restores the boat, producing an output glider in the same direction to the input glider.


In June 2013, Ivan Fomichev found a more compact century eater to replace the constellation comprising a beehive surrounded by three eaters:

#C Century eater replacing a four-object constellation in Paul Callahan's bistable switch #C x = 30, y = 43, rule = B3/S23 12bob2o$12b2obo2$10b5o$9bo2bo2bo$9b2o3bobo$15b2o16$28b2o$28b2o2$o$b2o$ 2o11$4b2o$3bobo$3bo$2b2o8b2o$12b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ THUMBSIZE 2 ZOOM 8 HEIGHT 480 WIDTH 640 ]]
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RLE: here Plaintext: here

In November 2017, Adam P. Goucher noticed that the century eater could be replaced by a century-to-glider converter, releasing another glider. By using Snarks to channel the gliders, this can be made into a gun as shown below:

x = 123, y = 93, rule = B3/S23 56b2o$55bobo$49b2o4bo$47bo2bo2b2ob4o$47b2obobobobo2bo32b2o$50bobobobo 35bobo$50bobob2o38bo4b2o$51bo38b4ob2o2bo2bo$90bo2bobobobob2o$64b2o27bo bobobo$55b2o7bo29b2obobo$55b2o5bobo33bo$62b2o$84b2o$85bo7b2o$85bobo5b 2o$86b2o25bo$111b3o$110bo$52b2o15b2o39b2o$49bo3bo15b2o$49b4o$118b2o$ 49b2o45b2o21bo$49b2o45bo22bob2o$97b3o11b2o4b3o2bo$99bo11b2o3bo3b2o$48b o67b4o$47bobo52b2o15bo$48bo52bobo12b3o$45b3o53bo13bo$45bo29b2o23b2o14b 5o$74bobo43bo$75bo42bo$118b2o5$9bo$9b3o$12bo$11b2o$85b2o$85bo$3b2o81b 3o$3bo84bo$2obo$o2b3o4b2o$b2o3bo3b2o$3b4o$3bo15b2o$4b3o12bobo34b2o$7bo 13bo14b2o18b2o$2b5o14b2o14bo$2bo32bo$4bo30b5o14b2o$3b2o35bo13bo$37b3o 12bobo$36bo15b2o$36b4o$34b2o3bo3b2o$33bo2b3o4b2o$33b2obo$36bo$36b2o$ 61bo$61b3o$44b2o9b2o7bo$45bo9bobo5b2o$42b3o10bo$40b3o$39bo$39b2o3$73b 2o$66b2o5bobo$66b2o7bo$75b2o$29b2o$28bobo5b2o24bo$28bo7b2o23bobob2o$ 27b2o32bobobobo$58b2obobobobo2bo$41bo16bo2bo2b2ob4o$37b2obobo17b2o4bo$ 36bobobobo23bobo$33bo2bobobobob2o21b2o$33b4ob2o2bo2bo$37bo4b2o64bo$35b obo71bo$35b2o70b3o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ AUTOSTART ZOOM 4 THUMBSIZE 2 WIDTH 640 HEIGHT 560 GPS 60 ]]
(click above to open LifeViewer)
RLE: here Plaintext: here

The over-unity variant of the bistable switch has a population of 32, lower than the original variant.

Memory storage

If a glider enters the switch when it is in the wrong state, the glider merely permeates through the device without affecting it. This means that any combination of input gliders, as long as they are sufficiently separated, will not destroy the device. This gives the conduit the ability to store information:

Let the inputs be called SET and RESET. The outputs can be designated SET SUCCESS, RESET SUCCESS, SET FAILURE and RESET FAILURE. The truth table is shown below:

Input Current state Next state Output

External links