guard, safety, safety device(noun)

a device designed to prevent injury or accidents

Safety Device

(a) A device to prevent overheating of any portion of a circuit by excess of current. It generally consists of a slip of fusible metal which if the current attains too much strength melts and opens the circuit. To ensure its breaking a weight is sometimes suspended from the strip. In one form an insulated German silver wire is wrapped around the end of the fusible strip a number of times and its end is connected to it. The other end of the German silver wire connects with the main lead, so that all the current goes through both in series. If the German silver wire becomes heated from excess of current the coil wrapped tightly around the end of the fusible strip melts it and opens the circuit. (b) Lightning arresters, q. v., may be cited under this heading. Synonyms--Automatic Cut Out--Safety Fuse, Plug, or Strip.

safety device

A device which prevents unintentional functioning.