Switch-Kat? I think you mean NCE's Switch-It?
I suspect that what's driving the signal may be contacts on whatever swicth machine the Switch-It is driving or that a stall-motor type swicth machine is being used, like the Tortoise.
With the Tortoise, you can wire in a pair of back to back LEDs. Depending on which direction the switch machine is thrown by the reversing polarity of the line it's fed by, the correct LED lights up. There is a diagram on how to wire that in the Swicth-It documentation, available as a pdf at this link: https://ncedcc.zendesk.com/hc/en-us/articles/202446835-Switch-IT-MK2
I suspect that the signal you saw was wired into the Switch-It like the LEDs are in that illustration near the end of that pdf.
Mike Lehman
Urbana, IL
hi
so i watch a youtube video of guy who had blma searchlight block signals item 4050 and nce switch-kat device. how he hook it up was one searchlight head was hook up to signal animator and the there searchlight head was hook up to switch though switch-kat. it neat cause when he though the switch the signal turn green to red and vicversa. now his layout is useing kato track. so i was wondering can i somewhat do the same thing with my bachmann e-z track switch. now i do have blma modern block signal dual head item 4035. and i also order new blma searchlight block signal with straght ladder item4070. and looking at ordering another one eather searchlight block signal with single head item 4071 or modern block signal single head item 4037 i donno yet. anyway is it possable if i find the right switch device decoder like switch-kat can i hook up the signals like in the pic i made.