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