Explanation

A Corkman was explaining the mysteries of Science and Telecommunications to his little son. 'The telephone', he told him, 'is like a big dog with his tail in Cork and his head in Dublin When you step on his tail in Cork, he barks in Dublin'.
"That's a wonderful explanation', said the little boy, 'now explain to me about the radio'
'The radio is exactly the same, my son', said the Corkman, 'but without the dog'.