AT Commands Reference Manual - wireless netcontrol GmbH

Call Control
If the other modem does not answer, the message "NO CARRIER" is received.
When voice call is established the voice is routed to the audio lines (Microphones, Speakers or
PCM) see more in Audio section. Once a voice call is active it is possible to send DTMF tones
using the +VTS command. It is also possible to prepare a DTMF string in advance within the dial
command, the tones will be sent once the voice connection established see below “Dialing to an
Electronic Telephone Service”. More details in the dial command “D”.
Circuit Switched Data - Baud Rate
Baud rate must be set higher than the network's rate.
Circuit Switched Data - Switching From Data Mode to Online
Command Mode
While in an active data call, to switch the connection from Data mode to Online Command mode,
send the Escape Sequence command (+++) or toggle the DTR line, while &D parameter is
configured to 1 a priori.
If the modem responds with "OK" to the Escape command, the modem is in Online Command
mode and the data connection is still active, but the AT command set can be used. To switch back
to Data mode use the “O” command.
Note: The character '+' in the Escape Sequence pattern can be changed using the S2 S-register.
Refer to “S, Bit Map Registers”, page 3-243.
As well the timing between each `+' can be controlled using the S12 S-register.
Escape is detected only by the H24 and not by the remote side. The remote side stays in
the Data mode.
Hanging Up a Circuit Switched call
Use the hang-up command ATH to release a CS call. The message "NO CARRIER" is received
indicating connection is closed followed by "OK". In case of more then one call (multi party)
involved pay attention to the different behaviors described in the ATH command and the +CHLD
command. For example in case of an alerting waiting call, hanging it up requires sending the
AT+CHLD=0 command, ATH just hangs up the active call.
To hang up an active data call, return to the Online Command mode by typing the Escape
Sequence, +++, and then hang up by sending ATH. A 2nd option is to toggle the DTR line, while
&D parameter is configured to 2 a priori.
Answering a Circuit Switched Call
Incoming call is indicated to the terminal in two options through toggling of the RI line and the
RING indication.
Extended information on the incoming call can be achieved using the +CRC (call type) command
and the +CLIP command.
Once alert is indicated to the terminal answering the incoming call is done by basic A command.
When answering a data call the modem negotiates with the calling modem to establish the
transmission speed and other parameters for the data connection. Successful negotiation will
3-10 H24 - AT Commands Reference Manual April 15, 2010