Audio Variometers for Club Rentals

if you're starting with a dated mechanical vario and no TE...

That's the point. We're talking 2-33s, 1-26s, etc. that have see a lot of
service and don't have batteries or TE probes.

I understand there are a lot of drawbacks compared to what one would have on
a private plane. I'm just wondering if portable units are a help or a
nuisance. Perhaps we'll get one or two, maybe different brands and see what
the reaction is.
Wad.