I heard a story that in the hot summer of 1976, a couple found that their phone was playing up. Sometimes it just refused to ring at all. The times it did ring, their dog would always bark before the telephone rang. And their dog had developed a sudden, strange aversion to going outside .....
How was all this connected?
They were on a party line, so the ringing voltage was applied between one leg of the line and Earth. Due to the dry conditions, the Earth connection at the base of the pole near the house was reading an abnormally high resistance; so there was a significant potential difference across the ground near the pole when the phone rang. When they were all sitting outside, the dog's lead was often tied to the telephone pole -- and that meant there was a significant potential difference between the dog's backside and its front paws ..... The poor animal had been getting electric shocks from the ringing voltage, losing control of its bladder, and in the process, improving the Earth continuity enough to make the phone ring!
Z.
