Computer-controlled advances in avionics, such as fly by wire, along with added onboard electrical features, including in-seat, passenger entertainment systems, are boosting electrical demand on board aircraft. Standard thermal circuit breakers and relay systems are carrying ever more current-dense wiring cables to provide this extra electrical power. In a legacy configuration, all related wiring runs directly between the circuit breakers and electrical devices. As a result, the as much as 100 miles (161 km) of wiring in a commercial passenger aircraft can be vulnerable to ground and arc faults, whether series or parallel, or actual current and voltage overload. This much wiring (as many as 50 circuit wires in a single wiring bundle) encompasses a huge maze for maintenance personnel to traverse. It also creates one of the greatest sources of heat in an aircraft cockpit.