Both ends uses Chan Lianshuang to accuse switch, and it is OK that intermediate use Shuang Lianshuang accuses switch, the switch inter among realizes the inverting of two electrical wiring to be connected, this kind of Shuang Lianshuang accuses switch bad to buy, and the price is very expensive, other accuse a truth more about the same also, ask attention: Allow aid igniter
Shuang Lianshuang accuses if switch is bad to search, can use Chan Lianshuang to accuse switch, 502 glue are used to be united in wedlock among, can let two Chan Lianshuang accuse switch one case so of linkage. 
Midway switch has 6 wiring aperture and 4 wiring opening two kinds
The first front line receives L, control line mixes, pull receive L in the 3rd box (control line that line the 2nd box rises twice) , the rest receives L1 L2 twice casually, 4 thrum across receives remnant of the 2nd box, the 3rd box, remnant both ends is received casually
