I have my safelights set up so that when I switch off the white light the safelight comes on and and vice versa and I also have a master switch that enables me to switch off the safelight only so that I can work totally in the dark, which I often do when I carry out a lot of work and extended development on the print. I did have 3 Duka 50 safelights rigged up in this way abd started to experience some strange fogging and paper discolourisation and tested every process and renewed chemistry etc before I was told by a company in the UK that when the Duka is first switched on it takes time for the lamp to warm up and if it is not at the correct temperature the paper will be fogged. I tested this and the paper fogged when I switched the lamp off for a few minutes and then switched it back on. When it was left on continuously there was no fogging. I ditched the 3 Duka safelights and now use 4 8 x 10 lamps with Ilford 902 filters that are amber and safe with most papers but there are more obscure papers that need a red safelight so I also have two of those just in case I ever need them.