Lucent Technologies MERLIN Plus Release 2 System Manual page 16

Summary
Voice terminal models BIS-34 and BIS-34D are ideal for the system
administrator/attendant console because their features allow you to easily use all
the system's features. You can also use the BIS-22 and the 34-Button Deluxe
models as the console. However, the SP-34, SP-34D, BIS-10, HFAI-10,
10-Button, and 5-Button voice terminals are not recommended for use as an
adrninister/attendant console because the administrator would be unable to see
which buttons were being assigned special features during system
administration. In addition, 10- and 22-Button voice terminals cannot be
used to program certain system features.
The MERLIN Plus Communications System 1-11