The target style signals at the Davis wye at one time had such upside down white on black colored triagular signs attached to them with the letters of "SA" and "P"? What did these letters mean?

And near the switch on the west side of the wye was an indicator type display signal that was slighly larger than a "dwarf" signal that had a miniture display inside of it of a "semaphore" but it wasn't actually one. What was this signal used for?

And speaking of semaphores for a time during the 1980's the Davis Amtrak Station had a red and a green light attached to the top of what appeared to be a large traditional "semaphore style" signal mast with lights posted in both directions right next to the station like the station in Petaluma did. What was the purpose of this signal?

And why is it now seem to be the case that some signals are always lit and some turn off when a train is not present in the area? Also, I have noticed that when one light on those two light signal posts is green one light always stays red rether than stying off like what used to be the case and that they now blink red and/or yellow when they are about to change. Did the UP reconfigure the signal operation when they took over operations from the SP when the buyout occured some ten years ago?

I seem to have noticed that those same lights turn a bluish white color when a switch into the siding movement was done. Was this light color unique to the old SP?

Is the northbound west valley line track from the Davis wye still in operational shape for a major freight or passenger train movement as it only seems to be used for switch movements these days? How busy is the Cal-P line through Davis compared to most rail lines in the United States?