Motorola V.34-SDC manual SDC Option Set 3-Sync Dial Only, X-SDC Dial-Only Application-Option Set

Configuring the Modem

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.

To 56/64 kbps

326XFAST

SDC NMS

Host

PSTN

326XFAST

SDC

DTE

Network Management Channel

Figure 4-3. 326X-SDC Dial-Only Application—Option Set 3

4-26 Configuring the Modem