The Overvolt Protection Unit "Powerline Guard" is the solution to protect expensive equipment from overvoltages. This small box is connected to the mains while your equipemtn is connected to the Schuko socket. In the case of overvoltages the box will switch off immediately (< 0,02 sec) the 230V from the schuko socket and an implemented piezo beeper will beep "SOS" as long as overvoltage is present. The Schuko socket will be switched on automatically when the mains line voltage is ok again. The trigger voltage range is adjustable with a small trim pot. A temperature switch switches off the Powerline Guard completely after about 4 minutes when overvoltage above 400 Volt are present for a longer time.