Installation manual

P a
r
a dyn e
1
COMSPHERE 3900 Series Modems
Models 3920
Plus and 3921 Plus
Installation Instructions
Document Number 3920-A2-GK41-10
April 1995
Overview
The COMSPHERE 392xPlus modems include an integral time division multiplexer (TDM) with a modem
sharing device (MSD) as standard equipment. The TDM provides time division multiplexing of up to four
independent ports over point-to-point lines using the V.34 family or V.32 family modulation. The MSD allows
multiple physical ports on a tributary modem to share a single communication channel using the V.34 family,
V.32 family or TMp modulation. These modems operate over leased-line or dial networks. The multiplexer (mux)
can be enabled or disabled to allow a greater degree of application flexibility. This document provides the
following information:
• Important safety instructions
• Regulatory notices
• Government requirements and equipment return information
• A description of the COMSPHERE 392xPlus models
• A list of equipment supplied with the modem
• A list of customer supplied equipment
• Installation instructions
This document is intended to be used in conjunction with the COMSPHERE 3900 Series Modems,
Models 3920Plus and 3921Plus, Installation and Operation Manual, Document No. 3920-A2-GN31.
Ordering Information
To order AT&T Paradyne documentation, please call 1-800-545-2354, extension 2222.