1
3980-A2-GZ40-20
November 1996
COMSPHERE 3800
Plus Modems
Synchronous Data Compression Feature
Document Number 3980-A2-GZ40-20
November 1996
Overview
The Paradyne proprietary Synchronous Data Compression (SDC) feature allows an increase of throughput in data
transmission, and has an error correcting procedure so that transmitted data is less sensitive to channel
disturbances.
The ITU-T recommendations V.42bis and V.42 have data compression and error correcting (EC) procedures for
DCEs connected to asynchronous DTEs. These procedures form the basis of Paradyne’s SDC feature.
With the SDC feature, two DTEs can exchange data via a synchronous protocol (Figure 1) while the DCE
provides the new synchronous data compression and error correction functions (Figure 2). The synchronous data
from the local DTE, after compression, is inserted into DCE frames which are sent to the remote DCE. Inverse
operations then occur at the remote DCE.
SDC can be used with V.34 and V.32 family modulations on dial or leased lines, and in a dial backup or standby
mode.
SDC is available as an installable option beginning with firmware Release 3.0.
SYNCHRONOUS
DTE
DCE
19.2 Kb/s
DCE
9.6 Kb/s
SYNCHRONOUS
DTE
19.2 Kb/s
SYNCHRONOUS PROTOCOL
495-14784
Figure 1. Sample DTE Exchange of Data via Synchronous Protocol and SDC
TM
