[emeritus]

Crowbar circuits are useful for equipment intended for use in the USA to cope with a not uncommon fault mode of domestic electricity installations where the customer is supplied via a transformer with a centre-tapped 240V secondary providing two 120V circuits. If the centre tap goes open circuit, both 120V circuits care connected in series, OK if they are equally loaded, but for example a high wattage toaster on one in series with a low wattage radio on the other would put over 200V on the radio, hence the desirability of crowbar protection in their light current appliances. It's a solution to a problem that doesn't usually exist in Europe.