Appendix B – Detailed Examples
Multi-Tech Systems, Inc. AT Commands for Wireless Modems with IP Connectivity (S000333D)
62
Answering an Incoming Call
This example cover the following: When an incoming call is received, the modem informs the attached equipment of the
call. The attached equipment then decides if the call should be accepted.
Description:
When receiving an incoming call it is possible for the attached equipment to either accept the call, to let
the modem answer the call automatically, or to not answer the call and then to let the modem
automatically call a pre-defined number using the ‘call-back mechanism’.
This application note describes how the attached equipment can instruct the modem to answer an
incoming call.
Configuration:
Configuration
•
The value of the PPPMODE parameter will determine the communication type: IP modem,
transparent modem,
•
ANSWERMODE must be configured in accordance with the ATS0 configuration for not
interacting.
•
RINGCOUNT must be configured for the number of rings before answering the call.
•
The CALLSCREENNUM parameter configuration with a decimal phone number need the
caller line identity service from the operator and the AT+CLIP=1 command sent to the
software
Automatic answer
deactivation
When the ANSWERMODE
parameter is set to 0, the modem lets the attached host decide
whether the incoming call should be accepted or ignored.
AT#ANSWERMODE=0
Operation:
Ring information
When receiving an incoming call, the modem informs the attached equipment via the serial port.
The modem issues a ‘+CRING:xxx’ message on the serial port for each ring signal received on
the GSM line.
+CRING
Caller ID
information
If the attached network subscription includes a caller ID service, the CLI (Calling Line Identity) is
understood by the software.
Depending on the telecom carrier, this service may be optional at an additional charge to the
subscriber.
+CLIP:”xxxxxxxxxx”,
Accepting the call
To direct the modem to accept this call, the attached equipment must send the ‘AT#ACCEPT’
command via the serial port.
The modem then goes off hook and attempts to establish the connection as specified in the
PPPMODE parameter (PPP client, server or transparent modem).
AT# command: AT#ACCEPT
Ignoring the call
If the attached equipment decides that the incoming call should not be answered, it should not
send the ‘AT#ACCEPT’ command via the serial port, the modem will, therefore, ignore the call.
Other AT# Parameters:
PPPMODE
Other AT# Commands:
CONNECTIONSTART
