Schindler HT buttons are obvious to spot as they have a distinct style. HT has a regular version and a VR version. I've always enjoyed this style of button because it's not like any others. So many modern buttons are all similar with no character to them.
This video shows in detail how a Schindler HT call button works and shows a method of wiring one up. I currently do not know how to use the original circuit boards to operate in the way which I want it to, so I designed my own way to get the buttons to light up. This video shows you a fairly simple way to get your button lighting up using very minimal materials.