Clive, when I broke in 1000 years ago, we had series st lts that we called arc circuit. It operated at a constant 6.6 amps with a voltage from 100 to 10000AC. Most if not all has been phased out where I was. The only experience I had on it really was retiring it. As for bypassing a bad bulb, the build screwed into a socket that plugged into the head, the socket had what we called a "pill" which if the bulb failed the pill melted closing the circuit.