Siemens 600 Series - Manual (Page 189)

Glossary G–5
status light. A light-emitting diode (LED) located next to every feature key
and line key on ROLMphone telephones, which indicates the state of that
feature or line. For example, the status light flashes next to the line key that
is on hold.
system feature. A feature of the CBX system that is available to all users.
T
trunk. A telephone line between a PBX and a local Central Office (CO).
Trunks are used when calling local or long distance numbers outside of
your company’s telephone system.