Drum as delay lines! Interesting that this is a magnetic drum used as set a of delay lines. Which sounds strange and convoluted: it doesn't use the permanent na

Drum as delay lines! Interesting that this is a magnetic drum used as set a of delay lines. Which sounds strange and convoluted: it doesn't use the permanent nature of magnetic storage. All data is read, erased and written back at least at every revolution. But using it this way allows storage speed hierarchy: There are long delay lines that take a whole revolution of the drum as intuitive. Then in between the read and the write-back of the long lines, there is a much shorter stretch of the drum that's used for very short delay lines - the entire track, as it rotates at the basic drum speed, is used to first write then read back a short section - recycled at a much higher cycle speed, many times at each rotation. Only one drum so necessarily the same single rotation speed is used as the medium speed for all delay lines. The same magnetic surface track / area is used for both kinds of delay lines. The long line - the manual calls it "line" - from "delay line?" - takes (most of) a whole revolution (21 such lines). And the same surface is also used for a bunch of "short lines" of several different lengths. Storage hierarchy that shares the same medium! The computer allows addressing with conceptual track / sector for the programmer but apparently that's done higher up in the system.