Motorola and V.32bis - Manual (Page 88)

4-26 Configuring the Modem
C
onfiguring
th
e M
odem
SDC Option Set 3—Sync Dial Only
In a typical dial application, a remote terminal dials the host for file transfers. This
allows remote users to dial in as needed, with a higher throughput than formerly
attainable over the PSTN. Alternately, the DTE and host (Figure 4-3) could be nodal
equipment (e.g., X.25 PADs, routers, bridges). In this configuration, the SDC
modems are used for remote dial-up branch connectivity. This is useful for remote
uploading or downloading data over the PSTN as needed.
Select SDC Option Set 3 for either of these applications.
Note the following:
• With Option Set 3, the modem provides the network timing (Clock=Internal).
• Specify the speed at which the modem communicates with the DTE using the
DTE Rate (AT * DE) option, to use a value other than the default. See the DTE
Rate description in Appendix A.
• With Option Set 3, the modem originates calls with its V.25bis ACU. DTR is
set to 108.1 so that an off-to-on DTR transition instructs the modem to connect
to the telephone line. If the modem detects an incoming call, the call is
connected. If the modem does not detect an incoming call and you have
enabled Default Dial (AT
* DA), the modem dials the number specified. If the
Default Dial (AT * DA) is disabled, the modem refers to the Mode option
(AT * AC). If set to answer, the modem goes off-hook and sends an answer-
back tone. An on-to-off DTR transition disconnects the modem from the
telephone line. If DTR is low, the modem does not auto-answer. DTR
transitions govern how the modem answers and disconnects calls.
• If you want the V.25bis ACU to manipulate the DTR signal, set DTR=108.2.
Other options in the ACU OPT’S category are set for a typical sync DTE.
• Select SDC Option Set 3 in both the local and remote modems, and ensure that
Mode (AT * SM) is set the same in both modems.
• The modem uses the adaptive rate feature in the V.34 Auto modulation mode.
This ensures maximum throughput when line quality is poor.
Figure 4-3. 326X-SDC Dial-Only Application—Option Set 3
PSTN
326XFAST
SDC
To 56/64 kbps
NMS
Network Management Channel
Host
DTE
326XFAST
SDC