An old theater of mine had a stage manager's Prompt podium that has a (SP/DT or DP/SP?) switch. In other words, it goes On/Off/On. Have the switch in one position and the podium lamp at 15w is a 15w lamp. Have the switch in the lower position and it's half the intensity. Given this is prime 1920's technology, how did they do this? It was also a metal podium, should I have been concerned if I spilled a glass of water? Given there was no ghost load lamps as below, what might be otherwise used to make this system work? The following is a possible way: (Fill in the blanks after study.) Short Circuiting Method of Dimming lights: Switch #A is the master Switch. Switch #B shorts group C and gives xxx to group #D. If switch #xxxxxx is open, Group C&D xxx in xxxx at 50% voltage and are thus dimmed. Any percentage of dimming or intensity is possible given the variations available in numbers of lamps and wattage between groups. Note: (not shown) Diagram Shorts Group C Sending 110v. To hot & Neutral wires in the circuit, what is effect this will have on the lamps, switch or wires? For all intensive purposes, the neutral should defiantly be treated as xxxx for grounding and insulating purposes. Thus lamp bases with xxxxx, or grounding to metal conduit should not be used. However, given power flows thru the path of least resistance, Lamps and metal equipment in general should be xxxx in Group #C. Do your best to post a diagram of how this all works.