AS 4852.2:2019 Variable message signs
5.1.4.1  General
Standard operation of the signs shall permit the simultaneous generation of alphanumeric characters for the number of lines, characters, and character heights as defined in Tables 5.1 and 5.2.
The sign shall be capable of supporting at least five fonts including the following two:
(a) Font 1 — standard height fixed font characters.
(b) Font 2 — standard height proportional font characters.
5.1.4.3
Justification Text messages shall be centre- and middle-justified by default, unless otherwise formatted using the relevant communications protocol.
5.1.5  Display changes
Display changes shall be effected by complete blanking of one display followed by delivery of the next required display. The sign shall permit flexibility in the selection of time functions such as blanking times, message display alternating rates, etc. These times shall be selectable via the control system, available locally and remotely from the specified host control centre.
The setting of a frame, message or plan, shall only be performed on inactive frames, messages and plans. An active message or plan shall run to full completion before a new frame, message or plan is activated. Full completion is considered to have taken place when the last frame of a message has been displayed for 10 s.
The sign shall:
(a) provide complete blank (i.e. all pixel inactive) and complete full screen (i.e. all pixel active) displays;
(b) successively flash the whole or any part of a display at a user-defined rate conforming with Table 5.4; and
(c) retain singular frames and/or messages in continuous display mode.
The sign shall accept text commands (i.e. set and display text frames) locally and remotely from the specified host control centre.
5.1.6  Dimming
The sign shall automatically adjust the output luminance of its display in response to external illuminance in accordance with Table 5.5. In the event that the sign’s light-sensing device(s) are faulty or non-functional, the sign shall dim the display to dimming level 3.
The sign shall include a minimum of two light-sensing units for dimming purposes.