PCB is one-sided, self etched layout of 22mm x 26mm in size.
[[Datei:PCB PiezoButton500dpi26x22.png|300px]]
Schematic:
[[Datei:FailButton1Circuit.png|600px800px]]
= Receiver =
A old version of an Arduino-Chime will be used to play amplified audio through big speakers. It is not clear if a an additional uC is used needed to receive the RF datamessage.