We used to have an absolutely fantastic museum called 'NINT' in Amsterdam, it had 10's of live exhibits like that and none of it was supervised. Then it got moved and half the collection was lost, then it was moved again and the lost the other half and now it lives on as NEMO, next to central station. It's still a nice day trip for younger kids but the hard technology angle has been almost entirely erased. Not that any kid today would understand what a rotary phone switchboard does anyway...