Allow every nth Herschel

[Extrementhusiast]

For this thread, use periodic circuitry. (Sorry, calcyman.) Instructions: Make a periodic conduit that if the conduit is phased correctly, then the Herschel completes the conduit, but if the conduit is not phased correctly, the Herschel is destroyed.

[calcyman]

If you're allowed gliders instead, this elegant mechanism by David Bell (1995) allows only p30-synchronised gliders to pass, and deletes all others:

x = 49, y = 49, rule = B3/S23
40boo$40boo9$10bo23boo$10b4o20bo$11b4o7bo9bobo3boo3boo$11bobbo6bobo8b
oo6b3o$11b4o4boo3bo14bo3bo$bboo6b4o5boo3bo15bobo$bobo6bo8boo3bo16bo$bo
19bobo$oo20bo$11bobo$11boo$12bo9boo4boo12b3o$22bobobbobo6bobo$14boo8bo
bbo8boo4bobo$14bobo6bo4bo8bo3b5o$14bo8bo4bo11boo3boo$23bo4bo11boo3boo$
25boo$$30bo$28boo$21b3o5boo$14bo6bo23boo$12b4o6bo22bo$11boboboo29b3o$
10bobbob3o30bo$10booboboo13boo$8b3ob4o14boo$7bobo4bo$7bo$6boo22boo$30b
obo$32bobbo$32bobobo$31boobobo$34boboo$25b3o6bo$27bo4bobo$26bo5boo!

[p46beth]

I suppose then, that the challenge could be completed by attaching David Bell's glider filter to a Herschel-->glider converter.

[calcyman]

I suppose then, that the challenge could be completed by attaching David Bell's glider filter to a Herschel-->glider converter.

Yes, along with a p30 (or a factor thereof) glider-to-Herschel converter. Doing so would be quite trivial, so I shall leave it as an 'exercise to the reader'.