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x = 13, y = 10, rule = B3/S23 3bo$2bobo7bo$3bo6b3o$9bo$9b2o3$bo$b2o$2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ AUTOSTART ]] #C [[ THUMBSIZE 2 WIDTH 600 HEIGHT 400 ZOOM 16 GPS 7 PAUSE 2 T 28 PAUSE 2 LOOP 29 ]]
Pattern type Conduit
Conduit type Converter
Conduit for R-pentomino
Converts to B-heptomino
Number of cells 5, 11
Step 28 ticks
Recovery time 33 ticks
Spartan? Yes
Discovered by David Buckingham
Year of discovery 1972

RF28B is a converter with several known forms, most of which were found by Dave Buckingham between 1972 and the early 1980s. It accepts an R-pentomino as input and produces an output B-heptaplet 28 ticks later. Of nine major variants known as of the end of 2017, four versions are shown below.

x = 18, y = 77, rule = B3/S23 8bo$7bobo7bo$8bo6b3o$14bo$14b2o3$6bo$6b2o$5b2o11$8bo$o6bobo$3o5bo$3bo$ 2b2o3$6bo$6b2o$5b2o18$6bo$6b2o$5b2o4$2bo$bobo$o2bo$b2o11$6bo$6b2o$5b2o 5$10bo$9bobo$9b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ AUTOSTART THUMBSIZE 2 GPS 7 ZOOM 10 HEIGHT 800 PAUSE 2 T 28 PAUSE 2 T 48 PAUSE 2 LOOP 49 ]]
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RLE: here Plaintext: here

The top variant above is part of the L156 Herschel conduit, but it can be replaced by the variant below it which produces a forward glider output. A B-heptomino naturally evolves into a Herschel, as shown above -- but it leaves an extra block behind which must then be cleaned up before the circuit can be used again. The third variant can be combined with a boojum reflector or rectifier to clean up this block.

In the other cases, a conduit such as BFx59H or BRx46B will normally be appended to the RF28B to suppress the creation of the block.

Note that flipping the loaf in the third variant and shifting it one cell down will yield the very similar looking RF48H. This is a completely different conduit, producing a Herschel without leaving the extra block.

The fourth variant above, consisting of a single boat, is the earliest one discovered (in 1972). It is used in Paul Callahan's Herschel receiver.

External links