AT&T MERLIN LEGEND System Reference Manual page 533

Hardware
Modems
For more information on modems and
modem pools, see the Data Guide.
Synchronous Features with Multipurpose Enhancement Board
RS-232 interface
half- or full-duplex operation using the RS-232 interface at data rates of 1200,
2400, 4800, 9600, and 19,200 using data transport Mode 2
half- or full-duplex operation at 56 kbps via the V-35 interface adapter cable
full-duplex operation at 64 kbps via the V.35 interface adapter cable
automatic answering of incoming data calls
ability to make outgoing data calls manually and select user-programmable
telephone numbers from the data module display on the front panel
RS-366 interface to an Automatic Calling Unit (ACU)
Synchronous Features with High-Speed Synchronous Enhancement Board
V.35 interface (the adapter cable is provided when the board is ordered by
using PEC 21624)
full-duplex operation at 48, 56, and 64 kbps
half-duplex operation at 56 kbps only
automatic answering of incoming data calls
ability to make data calls manually and select user-programmable telephone
numbers from the data module display on the front panel
A modem is used at an analog data station to make and answer data calls. It
converts the digital signals of the data terminal into analog signals for
transmission over standard telephone lines. It also converts incoming analog
signals to digital signals for acceptance by the data terminal.
Most types of modems can be connected to the system unless the modem is
being used in a modem pool. Hardware requirements for modem pools are
discussed later in this chapter.
If a modem is used with an MLX telephone, a Multi-Function Module (MFM) must
be installed in the telephone to provide a tip/ring interface for the modem. The
modem is connected directly to the MFM. If the modem is used with an analog
multiline telephone, a GPA is required to provide a tip/ring interface for the
modem.
When a modem is connected to an MLX telephone using an MFM, data calls are
dialed using the data terminal keyboard and voice calls are dialed using the
telephone dialpad. The MLX telephone cannot be used to dial data calls, and
the data terminal keyboard cannot be used to dial voice calls. Each device
operates independently, and features are assigned to each device
independently.
Adapters 5-27