Introduction; General; Description; Functional - Black Box 325 User Manual

2.1 General

The Modem 325 and Modem 325 Card are versatile, secure, and reliable modems that can operate full
duplex on both dial-up and leased lines. The modems are compatible with all required standards and
recommendations and offer a wide variety of automatic, remote, and backup capabilities. The most
notable characteristics are MNP
special features include a V.25 bis autodialer, secure operation, and trellis coding for improved signal-to-
noise performance.
The modem operates at data rates of
• 9600 bits per second trellis-coded, as stated in CCITT recommendation V.32
• 9600 and 4800 bps uncoded, as stated in CCITT recommendation V.32
• 2400 and 1200 bps compatible with CCITT recommendation V.22 bis
• 300 bps as stated in Bell specification 103*
Note: 4-wire leased-line mode supports 4800 and 9600 bps only.

2.2 Description

2.2.1 F
UNCTIONAL
The Modem 325 processes asynchronous serial data at 19200, 9600, 4800, 2400, 1200, or 300 bps, or
synchronous data at 9600, 4800, 2400, or 1200 bps, for transmission over the dial-up telephone network
and 2- or 4-wire dedicated leased lines. In 9600-bps trellis mode, near- and far-end echo canceling
combine with 8-state, 2-dimensional trellis coded modulation to maximize modem performance, even on
lines of reduced quality.
Integral test features allow the operator to determine system performance and isolate faults in the
communications link.
You can configure the modem from the front panel, or with AT or V.25 commands. Changes between
different modes of operation can be made easily and rapidly.
A security scheme prevents unauthorized access by a remote modem.
The V.25 bis autodialer broadens compatibility with host equipment.
2.2.2 P
HYSICAL
The modem is a standalone desktop unit. Operating options are stored in nonvolatile memory. A menu-
driven, 32-character LCD provides the operator with command feedback as well as real-time displays of
unit operation. Modem and DTE operation can be monitored by six LEDs and the display status screen
on the front panel.
Figure 2-1
The rear panel (
Figure 2-2
LINE connector, an 8-pin DIAL connector, and the power switch. The fuse and power cord are also on
the rear panel.
Inside the modem are two printed circuit boards and the AC line transformer. Hardware straps on the
main board offer additional options.
Note: If you ordered the MD278A-R2, you should have received cables with it.

2. Introduction

error-control protocols through Level 5 data compression. Other
®
shows the LCD front panel.
) has an EIA-232 connector for DTE interface, an 8-pin TELSET/LEASED
CHAPTER 2: Introduction
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