Danny.
The equipment you describe sounds very like a device called a mu-meter, which is actually still in use but in a very modified form. I must admit. I remember using it's predecessor, the Tapley meter. I still have the lumps on my forehead to prove it.
Spiney.
Last edited by Spiney Norman; 3rd Sep 2014 at 21:47.
Reason: My poor typing skills!