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Synchronous Modem Eliminator (SME-4M)
The SME-4M Synchronous Modem Eliminator is designed to replace two modems in point-to-point
applications. As shown below, a single SME-4M allows asynchronous, synchronous or bisynchronous
communications between two items of data terminal equipment (DTE) over EIA RS-232C cable.
In the synchronous mode, the SME-4M operates at speeds up to 38,400 bps, 56,000 bps or 64,000 bps
depending on the model. In either synchronous or asynchronous mode, the SME operates
transparently.
The small size and light weight of the SME-4M minimize logistics problems and simplifies installation
and replacement in the field. Since no special tools are required, the SME-4M unit is designed for
o-it-yourself installation.
Six indicators and three front panel switches facilitate operation and do-it-yourself troubleshooting.
The indicators (three for each item of DTE) monitor Transmitted Data, Data Set Ready and Clear To
Send signals. The front panel switches control Data Set Ready (DSR) and Ring Indicator (RING)
signals as well as select the digital loopback (DLB) test mode.
ASYNC OR
SYNC HOST
ASYNC OR
SYNC HOST
Figure 2-2. Typical Point-to-Point Application without Modems
6
2. Description
MODEM
Figure 2-1. Typical Point-to-Point Application with Modems
(ECN25C)
RS-232 CABLE
DIALUP OR
LEASED LINE
ASYNC OR
SYNC HOST
MODEM
ASYNC OR
SYNC TERMINAL
(ECN25C)
RS-232 CABLE
ASYNC OR
SYNC HOST
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