AT Command set summary for PCTel chipset
Zoltrix AT Command Manual For Zoltrix 56K HSP Models
Rev 1.0 10/9/1998

MODELS:
FMHSP56p         Internal K56Flex/V.90 Dual Mode Speaker Phone Fax/Modem (14,400 Fax/56,000 Modem)
FMHSP56PCI     Internal K56Flex/V.90 Dual Mode Speaker Phone Fax/Modem (14,400 Fax/56,000 Modem)

The commands listed in this document are for Zoltrix Modems based on PCtel's 56K chipsets.

AT Command Format

With the single exception of the A/ command, all commands to the modem begin with the characters AT, and end with a
carriage return character, hence the name AT commands. The general format of an AT command is: AT<command string>
where <command string> represents zero or more commands described in this manual. The <command string> can be null,
resulting in the simple sequence "AT". This sequence, often called the attention command, is useful for checking that
communication is established between an application program and the modem. The response to the AT command is always
OK, providing positive indication of proper operation. It may be useful to issue the AT command several times, with a brief
pause (100 ms. or so) between commands, until the OK response is received. Since the AT command string has no other
effect except to elicit the OK response, it can be used whenever the modem is in command mode. The AT portion of an AT
command can be in upper case or lower case, but not mixed case, thus AT or at, but not At or aT". The <command string>
portion is independent of case. The <command string> may contain space characters, which are ignored.

Your Zoltrix MODEM has been pre-set at the factory for optimum performance.
All defaults are set to allow the modem to negotiate the best possible connection with highest quality, data compression, and
error correction.

DEFAULT INIT STRING
The Default INIT string used at the factory and stored into the modem is as follows:

            AT&F&C1&D2
Because the modem was initialized at the factory, you could use an initialization (INIT) string of:

            ATZ

Note:   This command resets the modem to the stored settings. If the settings have been changed by software or manually,
this INIT string may not work correctly.

You could change the INIT string in all of your software packages to either of the two previous examples. The first example
is the best to use because some software may change the values stored in the modem.

If you want to custom configure your stored profiles, we suggest that you always start out with an AT&F&C1&D2 before
customizing other commands. This string will reset the modem to the factory defaults as well as reset some other basic
settings.

If modem performance suffers after modifying settings, send the INIT string above (AT&F&C1&D2) to the modem.

PERFORMANCE ISSUES

To get optimum performance from your Zoltrix MODEM, the phone line quality over which you are transmitting and
receiving must be reliable and relatively free of "noise". If you have very noisy lines you may be able to get a good connection by forcing the modem to connect at a lower speed. Refer to the S34 and S37 registers and Limiting the Modems Top Speed for information on controlling the modems speed.

LIMITING THE MODEMS TOP SPEED

If you experience problems connecting to slower modems (2400 or 1200bps), you may need to instruct your modem to limit the top speed to attempt. You may also need to limit the top speed the modem attempts to something less than 33,600bps,
even when calling another 33,600 modem, because of the line noise in your area. If you don't, you may experience "garbage" or a "NO CARRIER" message.
This should not be neccassary in most cases, but, there are some 2400bps and 1200bps or even 9600bps modems you may not connect to without using one of the following methods:
 
 

1. For connections or 14,400 and below, use the combination of the N0 command along with setting S37 to the proper value to limit the modems connection speed attempted.
2. Use the combination of the N0 command along with setting S37 and S34 to the proper value to limit the modems connection speed attempted.
3. Use the N0 command and set your software to the connection rate desired.

Note: Method #3 is not the desired method to use if you are making an error-correction connection with compression! The softwares "BAUD" rate should be at least twice, and preferably four, times the Carrier rate established. Otherwise you will get no benifits from the compression. Transfers will actually be slower than if a non-compression connection was established. You also cannot set software to all the connection rates that are supported by the 56K modem.
 

%P - PTT Testing Utilities

This facility testing of signal levels provides a continuous signal when the modem is in IDLE mode. This allows the user to initiate a series of signal that are necessary for PTT approval. These signals are answer tone, carriers, modulation, and other pertinent signals. A selected test will be terminated when any keyboard character is entered. The followings are command's description.

Note: For DTMF, the transmit level is -10dBm for low band and -8dBm for high band, inter digit delay is fixed at 70ms. All other transmit level is adjustable according to the setting of register S91 (from -10 to -15dBm). Speaker control initiates by command ATLn.
 

%I or %I? Country Code Selection and Identification

This command provides the ability of selection the desired country telephony Central Office. When the selection is correct, a set of the selected country parameters will be loaded for the current operation.