1.1. The light emitted by a sign must produce a luminous contrast which is appropriate to its environment, in accordance with the intended conditions of use of the sign, but without producing glare for an excessive amount of light or poor visibility as a result of insufficient light.
1.2. The luminous area emitting a sign may be of a single colour or contain a pictogram on a specified background.
1.3. The single colour must correspond to the table of colours and their meanings set out in paragraph 4 of Part I.
1.4. Likewise, when the sign contains a pictogram, the latter must comply with all the relevant rules set out in Part II.
2.1. If a device can emit both continuous and intermittent signs, the intermittent sign should be used to indicate a higher level of danger or a more urgent need for the requested/imposed intervention or action than is indicated by the continuous sign.
The duration of each flash and the frequency of the flashes of an intermittent illuminated sign must be such as to:
ensure the proper perception of the message, and
avoid any confusion either between different illuminated signs or with a continuous illuminated sign.
2.2. If a flashing sign is used instead of, or together with, an acoustic signal, identical codes must be used.
2.3. Devices for emitting flashing signs in the event of grave danger must be under special surveillance or be fitted with an auxiliary lamp.