When we wired plugs in physics at school, the earth pin had a rivet through it to prevent us plugging them in.
And the Cat 5 tester works using a shed-load of diodes in the remote unit. I think it works by pulling each pin high in turn with all the others low. Each pin as a forward-bias diode to all other pins (or just some others). Probably like this:
Although I would remove most of the diodes and do it like this:
And the Cat 5 tester works using a shed-load of diodes in the remote unit. I think it works by pulling each pin high in turn with all the others low. Each pin as a forward-bias diode to all other pins (or just some others). Probably like this:
Although I would remove most of the diodes and do it like this: