Appendix B – Detailed Examples
Multi-Tech Systems, Inc. AT Commands for Wireless Modems with IP Connectivity (S000333D)
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Automatic Answer of Incoming Calls
This example cover the following: When an incoming call is received, the modem validates the associated CLI (Calling
Line Identity) and if appropriately configured, can answer the call automatically.
Description:
When receiving an incoming call it is possible for the attached equipment to either accept the call, let
the modem answer the call automatically, or to not answer the call and then let the modem
automatically call a pre-defined number using the ‘call-back mechanism’.
This application note addresses the automatic answer mechanism implemented in the modem.
Configuration:
Configuration
•
The value of the PPPMODE parameter will determine the communication type for outgoing
and incoming call: IP GSM/GPRS modem, transparent modem, …
•
The GPRSMODE parameter allows to select the GPRS or GSM mode for outgoing
connection to the Internet
•
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
•
RINGCOUNT and ANSWERMODE must be configured in accordance with the ATS0
configuration for not interacting.
Automatic answer
activation
When this parameter is set to 1, the modem automatically answers an incoming call if the
associated CLI (Calling Line Identity) matches the CALLSCREENNUM parameter.
AT#ANSWERMODE=1
Caller ID validation When the GSM line subscription includes the caller ID service, it is possible to direct the modem to
validate the CLI (Calling Line Identity) of the incoming call before answering.
If no check is required, the CALLSCREENNUM parameter should be set to ‘*’.
AT#CALLSCREENNUM
Number of rings
The configurable number of incoming rings before the modem goes off hook to answer the call.
AT#RINGCOUNT
Operation:
Answering
When receiving an incoming call, the modem ignores the call if the associated CLI (Calling Line
Identity) doesn't match the CALLSCREENNUM parameter.
If the associated CLI (Calling Line Identity) matches the CALLSCREENNUM parameter, the
modem goes off hook and tries to establish a connection as specified by the PPPMODE
parameter (PPP client, PPP server or transparent modem).
Other AT Parameters:
AT#PPPMODE - GPRSMODE
