I recently purchased a 4-lens Adlake signal light for my collection. I applied 12-volt power to it and no go, so I opened the top and noticed that there is a (factory installed?) solonoid switch installed in series between the power cord (which seems original) and the 10 volt light inside. I then noticed the small hole near the bottom of the light where the lens to this light-sensor peeps out. I can't get the sensor to allow current throught, whether I apply light to it or block light from it. I can readily route around the sensor to hot wire it, but my question is why would such a signal light include a light sensor in the first place? Does it have a legitimate purpose in railroad operations? Do some signals only work at night or during daylight hours? i can provide pictures soon if I haven't explained it well enought.