Strange piezo drawing - anyone understand it?

Hi to all,

Its a rainy day here and I thought I would finally get round to making a few circuits I have been meaning to try for ages.

I came upon a circuit for a Piezo buzzer on the web and was just going to build it when I noticed that it has, or seems to have 3 connections on the piezo element!

Are there 3 pole piezo elements or is there something I'm missing about the drawing?

Thanks Al

We use a three wire piezo element in our alarm box, different combinations of wiring give slightly different tones. I think this is the type used in the diagram.

hi Al, [ hows the weather]

Its a self resonant piezoelectric , the small plate is the positive feedback/sense element for the sounder to work.

Eric

Hi Eric and Ian,

Thanks guys for clearing that up.

Eric, the weather is dismal here, well more than usual anyway hehehe.

Could be worse though I have a mate who is now on his 8th day of a 21 day trip around Scotland CAMPING!

He can afford to complain about the weather!

Regards Al