An extension line (also extension cord , extension cord , or short extension called) is a cable that can be connected when the length of the own connection cable of an electrical device is not sufficient, or other connection line.
However, a power line (power cable ) must not be lengthened at will, as short-circuit detection by the fuse is no longer guaranteed due to the higher intrinsic resistance of a line that is too long and, under certain circumstances, there is a risk of fire and death for the user in the case of defective end devices. This applies in particular to the loop resistance of the protective conductor connection; it limits the cable length to the usual 50 m for cable reels, for example. If there is a high current flow through the cable, it is advisable to unroll the cable completely to prevent overheating (due to accumulated heat) or a cable fire.
The term extension cable not only refers to power cables, but also cables for data transmission , for example:
- Network cable
- USB cable
- Audio cable
- Telephone cable (analog)
- ISDN cable
- Centronics cable
- SCART cable
- Antenna cable
Since some electrical signals cannot be transmitted over any length of distance, extension cables are often subject to physical limits. For example, the maximum length for USB cable connections is 5 m, unless the transmitted signals are amplified via an intermediate amplifier.