On 9 Apr 2018 at 11:59, RussellMc wrote:

> In time "high tech" solutions included "NIR"s (Negative impedance repeate=
r)
> (Negistors?) made initially by Philips if memory served, which were
> adjustable to balance cable impedance appropriately when magically adjust=
ed
> correctly, or to make the circuit sound hollow and echoy or even to
> oscillate on other occasions.

Yip, Philips negistor. I'm not old enough to know about them, but recently =
read an=20
interesting article. Written by a friend & former work colleague, one page,=
 page 9:

http://www.nzart.org.nz/assets/breakin/current/01_BreakIn_JanFeb2016.pdf

--=20
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