Nortel Meridian SL-100 Reference Manual page 71

Key-based Access Expansion Module (KBA)
The KBA has 22 keys which can be used as additional keys to the physical and
self-labeled programmable feature keys on the M3900 series sets. These
additional keys can be used as DN or feature keys. The sets and modules attach
in such a way as they look and feel like one integrated unit. The M3904 and
M3905 sets use the KBA.
There are 32 keys on the M3904 and M3905 sets. The M3904 and M3905 sets
support one or two KBAs with 22 keys each. With one KBA, the key numbers
are from 1 to 54 with the first key mapping to key number 33. With two KBAs,
the key numbers are from 1 to 76, with the first key on the second KBA
mapping to Key 55.
Note: A KBA cannot be combined with the Display-based Expansion
Module (DBA). A KBA can only be used with the M3904 and M3905 sets
and is provisioned through SERVORD commands.
Figure 9-1 shows the KBA.
Figure 9-1 Key-based expansion module accessory
Display-based Expansion Module
The DBA is an optional add-on module for the M3904 and M3905 sets
exclusively. The module attaches to a Meridian digital set to increase the
number of programmable feature keys on the set by 24 for a total of 56 keys.
The DBA has keys 33-56 supporting up to 3 layers of 8 programmable feature
keys. It has eight self-labeled keys with the feature labels next to the key. A
paging fixed-key allows switching between the 3 layers of self-programmable
feature keys. The labels change according to the features programmed for the
MSL-100 M3900 Meridian Digital Telephones Reference Guide MSL15
Hardware options 9-5