US Soft Touch
These buttons were used in late U.S. Elevator installs and were definitely an interesting fixture. Instead of being a regular push button, these were more of a "touch sensitive" style of button, though they are actually pressure sensitive. There are also regular push button versions of these buttons. This video shows the wiring of a soft touch button.
Wiring these buttons is really simple. You need a 24V DC supply. The + from the source goes to S2. S1 is connected to L2. L1 is connected to the - of the power source.