A circuit that has stopped working can still contain live parts. Safe isolation means disconnecting the relevant supplies, preventing reconnection and verifying absence of voltage at the parts involved before work.

This lesson explains the safeguards so you can recognise an incomplete method. It does not establish practical competence to expose or test mains conductors. If you do not already have the training, suitable equipment and ability to carry out the complete method safely, use a registered electrician.

Never work on live household wiring. A lamp going out, a switch position or confidence in a circuit label cannot replace the verification.