A danger aspect is usually the red aspect shown on signals. In some signals, especially shunting and other special purpose signals, another colour may be the danger aspect.

See also:

Proceed aspect and caution aspect

The area of rail the standard gauge network controlled and operated by ARTC.

A DMU or a diesel multiple unit is a diesel-powered train of multiple carriages (typically seen as a non-suburban or inter-city train). A DMU does not have a separate locomotive but uses (one or more) diesel-powered railcars (cars). Motorised cars ("M" cars) are usually semi-permanently coupled to non-motorised trailer cars ("T" cars) forming a "unit". Two or more units create a set.

e.g.  an MTM unit consists of a traction car, a trailer car and another traction car, all semi-permanently coupled.
        an MTMMTM set consists of two MTM units coupled together for a given period of time

A single diesel-powered railcar may generally be classed as a DMU (even though there is only one car).

See also EMU.

dc = direct current, as found in batteries

The Designated Interstate Rail Network (DIRN) is the vast majority of main line standard gauge railway lines on the mainland of Australia, owned, leased and maintained by ARTC.

A display panel is a piece of hardware used by signallers to show the position of trains and the state of signalling equipment in the area of control.

A distant signal (or approach signal) is a signal that advises the status of the next signal. The signal has two aspects, caution (yellow) and clear (green).

If the distant signal is clear, the next signal is not at danger (least restrictive). If the distant signal is at caution, the next signal is at danger (most restrictive). 

Distant signals are used where the driver would not be able to see the main signal in time to stop (i.e. where the main signal is around a bend or after a tunnel, or where the train is very heavy or fast and needs a large braking distance).

Distance signals are placed sufficient distance from the main signal to suit the worst-braked train (fastest and/or heaviest) that uses the line.

Down local. Refers to the train that is on, or to the track itself, that carries the local traffic (around the station) in the down direction. 

See also up local. 

In most countries — but not all — a train travelling in an "down" direction is travelling away from the capital city. Where a train travels between two regional cities, one may be designated the down direction.

The train is often referred to as a down train (i.e. the 13:45 down train).

The signals that face this train are often called down signals.

Also see up direction.