The permanent cabling and fittings in your home are called electrical installations. A licensed electrician generally carries out work on electrical installations and fittings. Electrical installations can age and become overloaded, particularly in old homes where the original wiring was not designed for the number of electrical appliances in use today.
Warnings signs that the installations in your home are becoming dangerous include plugs and sockets that are hot to the touch or have brown scorch marks on them, fuses that blow, circuit breakers that trip for no reason and flickering lights. These signs may mean that the wiring in your home needs upgrading. If you are concerned, contact a licensed electrician.
When buying a house, or if you notice any of the above warning signs, have a licensed electrician or electrical inspector check the internal wiring. They will be able to tell you if repairs are necessary and estimate the cost.