AT&T MERLIN LEGEND Release 2.0 Equipment And Operations Manual page 230

Data Communications Support
Modem Pool Configurations
Figure 5-1 shows three modem pool configurations:
1. Digital-to-analog modem pool, which enables a digital data endpoint to
originate a call to an analog data endpoint. In this configuration, the
7500B Data Modules are assigned to a DHG.
2. Analog-to-digital modem pool, which enables an analog data endpoint
to originate a call to a digital data endpoint. In this configuration, the
modems are assigned to a DHG.
3. Digital-to-analog modem pool on dedicated outside lines, which
converts digital signals to analog signals for data calls from a digital data
station to an outside analog data station. It does this over analog
dedicated outside lines used solely for data communications. In this
configuration, the 7500B Data Modules are assigned to a DHG.
Configurations 1 and 2 (digital-to-analog and analog-to-digital) use system lines;
therefore, the modems and 7500B Data Modules are connected directly to the
control unit. Each modem is connected to a jack on a 012 or 008 OPT module,
and each 7500B Data Module is connected to a jack on a 008 MLX, 408 MLX,
or 408 GS/LS-MLX module (Release 2.0 only).
In configuration 3 (digital-to-analog on dedicated outside lines), the 75006 Data
Module connects to the control unit via jacks on a 008 MLX or 408 GS/LS-MLX
module (Release 2.0 only).
In all three configurations, a 440A4 terminating resistor is required because the
7500B Data Module connects directly to the control unit. Also, each
modem/7500B Data Module pair requires a null modem connector to
interconnect the RS-232 interfaces of the modem and 7500B Data Module.
The 7500B Data Modules or modems in modem pools must not share a port
with an MLX telephone. Otherwise, the telephone could use both B-channels
and block use by the 7500B Data Module or modem.
Other Resource Pools
Users can share a limited number of modems or 7500B Data Modules
connected to a shared data endpoint. To do this, the communications system
can be configured for modem-only or 7500B Data Module-only resource pools.
The modem-only pool can provide access to multiport data equipment, such as
a local host computer, by assigning the T/R ports interfacing with the modems
in the pool to a DHG.
Like the modem-only pool, the 7500B
access to multiport data equipment, such as a host computer, by assigning the
MLX ports interfacing with the 7500B Data Modules in the pool to a DHG.
5-12
Data Communications Configuration Overview
Data Module-only pool can provide