On 22 Oct 2004 05:36:12 -0700, (bell) wrote:

Hi, Does anyone know what's inside one of these?

It's a bit of kit to link up two boiler systems. My dad's doing a self
build and he's going to need one but is curious as to how they work.

Thanks x

Google for it, there's quite a bit, including diagrams. Might help
you.