AT&T MERLIN LEGEND Release 2.0 Equipment And Operations Manual page 124

Hardware Components
NOTE:
The quality of speakerphone transmission can be affected by equipment in
the area of the microphone.
Specialty Handsets
Handsets for users who are hard of hearing (model K6S) are available for use
with MLX telephones.
Message
The Z34A message-waiting indicator can be connected to single-line sets that
do not have a Message LED.
Additional Telephone Adjuncts
The following adjuncts also can be connected to telephones:
Answering machines
Credit card verification terminals
PCs (connected through modems, 75006 Data Modules, or directly with
a built-in modem)
Adapters and Adjuncts Not Supported
CAUTION:
The following analog telephone adjuncts and adapters cannot be used
with the system and in some cases will damage the device or the
system if connected:
Basic Telephone and Modem Interface (BTMI)
Basic Telephone and Modem interface-2 (BTMI-2)
ATR Interface (ATRI)
MTR Interface (MTRI)
Off-Premises Extension Unit (OPU)
System 25 Direct Extension Selector (DXS)
2-50 Adapters and Adjuncts
Waiting Indicator