What is a safety devise with a switch?

Answer 1

Ask a vague question, get a vague answer: In a wall switch, the safety features are: Plastic casing insulates user from current. Metal parts are earthed to take current away in a malfunction. Safety devices using switches include: Extractor to remove dust and fumes from a workshop Sound sensitive ear-defenders (switch is automatic- if sound level reaches maximum, sound is no longer relayed) Welders mask with liquid crystal visor- when light level is too high, switch turns on and visor becomes less transparent. Fireman's sensor- if the body doesn't move for 2 minutes, a switch causes the sensor to make a loud sound, alerting the rest of the crew to an unconscious colleague.