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Configuring the Modem 4-23
Configuring
the Modem
When used as a restoral device for Telenetics and Motorola 35XX DSU/CSUs
(Figure 4-1), select SDC Option Set 2 in the local and remote SDC Modems. This
places the modems in external timing, as digital services typically provide the network
timing.
Figure 4-1. Single Channel Point-to-Point Digital Link Restoral (A/B Switch)—Option Set 2
Note the following:
• With SDC Option Set 2 selected (for Telenetics, Motorola, non-Telenetics, and
non-Motorola DSU/CSUs), the DSUs’ restoral configuration should be set to
Timing=Internal.
• In this case, the 326XFA S T-SDC DTE Rate must be set to a constant rate as
provided by the network (defaults of 56/64 kbps).
• Enable Option Set 2 in both the local and remote modems, and ensure that Mode
(AT
*
SM) is set the same in both modems.
• The SDC modem supports single channel environments only. For example, the
SDC modem can restore Port 1 only of the 35XX device.
• The 35XX device, when initiating restoral, must be set to Normal mode (as the
35XX network management channel is virtually a time division multiplexed data
stream which cannot be compressed with the SDC product).
• The SDC modem may have the ARS feature enabled. In this case, ARS
determines the link rate.
35XX
56/64 kbps
PSTN
Router
35XX
Router
To 33.6 kbps
NMS
Network Management Channel
To
56 kbps
326X
FAS T
SDC
326X
FA S T
SDC