Safety Devices
Electricity and water don't mix! While most of us are very careful about using electrical appliances in bathrooms, outdoors, and in damp basements, accidents do happen - and with electricity, the results can be a fatal shock. To provide additional protection from shock, electrical codes require special devices called GFCIs (ground fault circuit interrupters) when outlets are located near wet areas like kitchen counters, bathrooms, basements, garages, and outdoors. These devices automatically shut off the current when they detect a possible shock hazard.
A newer device, called the AFCI (arc fault circuit interrupter) can detect sparking wires, and shut off power more quickly than a standard circuit breaker.                
Most people won't debate the necessity of smoke detectors in the home. But did you ever wonder if you would hear the basement smoke detector from your bedroom? Interconnected smoke detectors can be wired throughout the house. When any one of them detects smoke, all connected units sound the alarm. These units are powered from a household 120V circuit, so they don't need batteries to operate. Some models can be interconnected with carbon monoxide detectors to provide additional protection.
The electric company delivers power to homes through a service, which includes a heavy cable that connects the home to the utility's wires, a meter enclosure, a circuit breaker panel, and the grounding system.
An electrician sizes a service according to the electrical demand of the home. 100 amps will serve most homes, while others may require 200 amps.
When is it time to replace a service? A service less than 100 amps is no longer considered adequate for a home, and should be upgraded. When the outer jacket of the main cable frays, rain can enter the system and create serious trouble. Fuse boxes are also problematic when they are part of a service because it is very easy to oversize fuses to the house wires. Overheating and fire are the unfortunate result in many cases. Many fuse boxes are also too small for the needs of a modern home, and don't provide enough spaces for needed circuits.
Additional wiring
Extension cords are not substitutes for adequate wiring outlets! Their insulation can quickly degrade, allowing wires inside to spark. Heavy appliance loads can also cause an extension cord to overheat!  Permanently wired, grounded outlets are the safest way to connect kitchen appliances, air conditioners, electric heaters, and irons to power.
What is knob and tube wiring?
For more information about home wiring, see this page