The life saving device which offers a level of personal protection that ordinary fuses and circuit-breakers cannot provide tripped when it sensed an imbalance between the neutral and earth wires. This fault within a socket in a family home was thankfully detected by the RCD before the cable hole increased through time and touched and exposed the red live wire where the potential of shock and fire risk would have greatly increased.
RCD's are now a very important requirement of current electrical regulations where most if not all circuits within a home should have RCD protection.
Further information on RCD's can be found at the weblink below and here at SES we offer free estimates in most circumstances if you would like us to quote for the replacement of your old fusebox with a new safer life and premises saving RCD consumer unit.
http://www.electricalsafetyfirst.org.uk/guides-and-advice/electrical-items/rcds-explained/