Velleman К8075 - Manual (Page 10)

10
Wiring the push button
In case you want to use a different push button, make sure it is rated for the AC-voltage.
If you do not use the included push button, you can mount a 3mm LED on the PCB.
COLOR= 2...5
LD...
CATHODE
Watch the polarity !
Do not use both simultaneously
(LED & included push button)