Internal Wiring
A wiring is mechanically protected when it is enclosed within the casing of an apparatus or when it is protected by equivalent systems.

Definitions of employment
Indoor use:
The cable is installed or connected to an appliance and is located permanently within the building in ‘ “expected environment.” The building can be used for residential purposes, commercial or industrial.

Temporary outdoor use:
The cable can be used outside in ‘ “planned environment” for short periods.
Examples include: connection of small household appliances such as electric drills or lawn mowers, etc.

Permanent outdoor use:
The cable is designed to withstand the various stresses (including bad weather) that may occur to the outside in ‘ “expected environment.”

SERVICE CLASSES
The service is the application of a type of flexible cable, in relation to the possible combinations of the type of use or of the relevant external influences to such use.
The specifications for the individual devices indicate cable types suitable for each unit.
With particular regard to mechanical external influences, and in general terms, the “Service” is here calssificato into 4 categories as follows.

Extra light service
When the risk of stress and mechanical damage is negligible, that is, in the presence of external inluenze that is to be expected during normal operation of light equipment in the home or in the office, and when a flexible cable with a greater degree of mechanical protection may prevent movement of the appliance or in any case give rise to a number of limitations of the use envisaged.
Such devices may be electric shavers, electric clocks, etc..

Light Duty
When the risk of stress or mechanical damage is low, as is to be expected in normal light or mobile portable appliances used in homes, offices and shops.
Such devices may be domestic dryers and equipment for hairdressers, radio sets, table lamps or other of the table and small office equipment.

Full service
Generally when the cables are subjected to light mechanical stresses and the risk of mechanical damage is low, as is to be expected in normal use of small and medium equipment in domestic, commercial and light industry.
Such devices may be toasters, small appliances for the kitchen, vacuum cleaner, washing machines, sewing machines and refrigerators.

Heavy duty
When the risk of stress or physical damage is medium size, as is to be expected during normal operation of equipment for the media industry, for agriculture or for temporary use on construction sites.
Such devices may be portable lamps, heating plates, large boilers, small motors or to construction sites and agriculture machinery, lifting equipment and fixed installations in temporary buildings.

Heavy duty (only for multi-core cables)
As cables for heavy service, but used mainly for interconnections between parts of machinery used for the manufacture, including machine tools and mechanical maintenance of equipment. They can be used inside or outside of buildings where the ambient temperature is between -25 ° C and +25 ° C, and in permanent service with conductor temperature not exceeding 60 ° C.
This type of usage can be eg. the connection of a control unit to a machine such as eg. a crane or a hoist, or the interconnessionedi a control desk with a machine for the industrial manufacture when the cable length is not more than 10 m. longer lengths are acceptable when cables are used for fixed interconnections.

NOMINAL TENSION
The nominal voltage of a cable is the reference voltage for which the cable is designed and which serves to define the electrical tests.
The nominal voltage is the combination of two Uo / U values expressed in Volt:
Uo is the rms value between any insulated conductor and earth
U is the effective value between two phase conductors of a multiconductor cable or the single core cable system.