codefag
numerologyfag
mapfag
Referred by a fine anon to this, if helpful
He instituted an elaborate internal communications
system to reduce the sense of isolation that their captors tried to create, which used a five
-by-five matrix of tap codes for alpha characters. (Tap-tap equals the letter a, tap-pause-tap-tap equals the letter b, tap-tap-
pause-tap equals the letter f, and so forth, for 25 letters, c doubling for k.)