Interesting part

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Sat Jun 12 16:18:12 2004

> Probably just a "standard" mercury delay line. The RL11 I've got behind me
> uses one for its write precompenstation, and there are usually lots of

Actually, the RL11, and all other disk controllers (which use them for
precompensation), DRAM cards (which often use them for producing the
RAS/, CAS/, MUX signals in the right sequence, etc) use
inductive/capacitive delay lines. They are purely electrical, and don't
depend on mechanical pulses in a medium, like mercury.

> them in "older" video equipment (like 70's or early 80's). They do what

UK PAL video equipment used to use a glass delay line as part of the PAL
decoder. This was a 'mechanical' device -- piezo-electric transducers
sent a pulse through the glass which was picked up about 64us (a little
less -- just under 1 line time) later by a similar transducers. Old VCRS
-- the better ones anyway -- used a 64us (exactly 1 line time) delay line
to store a video line to be used if there was a dropout on the tape.
Modern ones don't seem to bother :-(

I have often wondered about using such delay lines for data storage...

-tony
Received on Sat Jun 12 2004 - 16:18:12 BST