[ThePillenwerfer]

Here's the Continuity Tester circuit as promised. I hope it's clear enough as I haven't had to draw one neatly for two-and-a-half decades! Mind you, I couldn't tickle them up on a computer then.

There's no need to get hung up on the speaker impedance as over the years I've used everything from 8Ω to piezo transducers.

Mine has got an 80Ω one along with a socket so I can use this a high (ish) impedance test speaker. I keep meaning to add another one so I can use the tester's output as a crude signal generator but on the rare occasions I've wanted such a thing have just put jump-leads on it.

Basically the higher the tone it makes the lower the resistance it's testing. Very high resistances will produce a series of pips and it's surprising how it can be pipping every couple of seconds on things that other meters have read as infinity.

I hope other people find it as useful as I have.

- Joe