====Equipment Reference Numbers====

Equipment Reference Numbers are also often known as //ERNs// or informally as //Tag Numbers//.

They are a unique alpha-numeric sequence that identifies a specific asset. 

They often follow a strict structure giving some information as to what the asset might be - for example, the //PT// in the ERN **PT105** may mean 'Pressure Transmitter'.

The ARDI documentation avoids using the term 'Tag Number' as it causes some confusion - users could find themselves confused between '[[tags|tag]]' and '[[ardibasics:ar_marker_tags|AR marker]]'. 

So the more generic "Equipment Reference Number" or **ERN** is used throughout the documentation.