Iwatsu Omega-Phone Adix APS Owner's Manual page 168

An optional Busy Lamp Field (BLF) may be added to the Attendant Console.
The Busy Lamp Field has 200 lamps to provide status indication for the
system extensions and outside lines.
The Attendant Console has all the capabilities described in the Digital
Telephone User's Guide. Many feature operations in the Digital Telephone
User's Guide require the pressing of the Speaker button (SPKR) to start and
end feature operation. The Attendant Console does not require the use of the
Speaker button (SPKR) to start feature operation, but does require pressing
the Release button (RLS) to end feature operation. The maximum number of
DSS Units and Attendant Consoles may not exceed eight.
ATTENDANT CONSOLE (Fig. 1)
ATTENDANT CONSOLE USER GUIDE - 154