User guide

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Chapter 5 - AT Commands
S154: B-Channel Answer Rate
Usage: S 154=n; S154?
Unit: Decimal ASCII code
Range: n= 0 (64Kbps, but use Progress Indicator IE),
n= 1 (64Kbps, ignore Progress Indicator IE, check Bearer Capability IE),
n=56 (54Kbps),
n=64 (64Kbps)
Default: 0 (64Kbps, but use Progress Indicator IE)
S154 allows you to force the TA to answer digital calls with a 56Kbps or 64Kbps B-channel
rate. In some situations, it is necessary to force a 56Kbps connection, as, for example, when a
call fails to connect because the end-to-end connection is not 64Kbps and the originating TA
or the answering TA is not informed of this situation by the network. In some situations it is
necessary to force a 64Kbps connection when the TA is first informed that the call changed to
56Kbps but then later returned to the ISDN and switched back to 64Kbps. It may be more
likely that setting S154=1 is the best solution to the “not end-to-end ISDN” message given by
the network. In this case (S154=1), the TA will assume 64Kbps unless the Bearer Capability
Information Element indicates a 56Kbps connection. The TA will then ignore all Progress
Indicator Information Elements when S154=1. By default the TA will check for Progress
Indicator Information Elements indicating changes in the routing of digital calls to determine
whether the call needs to switch to 56Kbps or remain at 64Kbps.
Using AT Commands to Operate the
Terminal Adapter
You can configure and operate the Terminal Adapter entirely with AT commands, if you want. Remember, you
can issue AT commands only from a terminal or from a computer running a communications program in terminal
mode. This section describes how to use AT commands for basic operations such as calling, answering a call,
and hanging up.
Modes of Operation
The TA has three modes of operation: offline command, online command, and data.
Offline Command Mode
In offline command mode, the TA communicates with the terminal or computer and responds to AT commands.
There is no data communications link with a remote device.
Data Mode
The TA enters data mode when it makes a successful data communications link with a remote device. In data
mode, the TA can send and receive data, but it does not respond to AT commands. Instead, it treats them as data,
and transmits them to the remote device.
Online Command Mode
In online command mode, the TA responds to AT commands while maintaining a data communications link;
however, transmission of data is suspended. To enter online command mode from data mode, type the escape
sequence +++AT<cr>. To return to data mode from online command mode, type ATO<cr>.
Making a Call
Before you can place a data call, you must configure the TA for the local switch type, serial port speed, and the
data type of the ISDN device you want to call.