> 2.9.3 | CSD call handling – incoming calls

> This section comprises the subsections Description, Used AT Commands, Flow Chart, Hints and Example. To move to these subsections please use the Navigation Frame or the appropriate buttons on the toolbar.

> 2.9.3.1 | Description

> This chapter describes the handling of incoming CSD calls.
> Depending on the basic initialization, an incoming CSD call is indicated either by the URC “RING” (if AT+CRC=0) or the extended URC format “+CRING: REL ASYNC” (if AT+CRC=1).
> An incoming data call can be accepted by entering the command ATA or by using the autoanswer mode if enabled with ATS0≠000. Depending on the module's basic initialization, connection setup is indicated by the result code "CONNECT" (if ATX0) or "CONNECT <text>" (if ATX>0), where <text> gives the transmission speed, for example "CONNECT 9600/RLP". In addiditon, the CONNECT result code may be preceded by the intermediate result code “+CR: REL ASYNC” if the ME is initialized with AT+CR=1.
> In example 3, subscriber 1 has initialized the ME with ATV\0 to suppress the RLP trailer in CONNECT result codes. Note, that some products do not support this command. Subscriber 2 uses the full result code format including text and RLP trailer.

> 2.9.3.2 | Used AT commands

> Command | Explanation
> ATA | Answer a call
> +++ | Switch from data mode to command mode
> ATO | Switch from command mode to data mode / PPP online mode (PP online mode applies to GPRS connction only)
> ATH | Disconnect existing connection
> AT+CHUP | Hang up call

> For further details about the commands see [2].

> 2.9.3.3 | Flow chart

> Figure 55: CSD call handling - incoming calls – part 1
> Figure 56: CSD call handling - incoming calls – part 2

> 2.9.3.4 | Hints

> Not applicable.

> 2.9.3.5 | Example

> Example 1:
> ***************************************
> Comment: CSD call handling - incoming call – reject
> ***************************************
> ***************************************
> Comment: Subscriber 2 makes CSD call to subscriber 1.
> ***************************************
> Subscr 2 Send: ATD2400022
> Subscr 2 Receive: ATD2400022
> Subscr 1 Receive:
> Subscr 1 Receive: +CRING: REL ASYNC
> ***************************************
> Comment: Subscriber 1 rejects the incoming CSD call.
> ***************************************
> Subscr 1 Send: ATH
> Subscr 1 Receive: ATH
> Subscr 1 Receive: OK
> Subscr 2 Receive:
> Subscr 2 Receive: +Cause: 8:21
> Subscr 2 Receive: NO CARRIER
> Example 2:
> ***************************************
> Comment: CSD call handling - incoming call: Answer CSD call manually.
> ***************************************
> ***************************************
> Comment: Subscriber 2 makes CSD call to subscriber 1.
> ***************************************
> Subscr 2 Send: ATD2400022
> Subscr 2 Receive: ATD2400022
> Subscr 1 Receive:
> Subscr 1 Receive: +CRING: REL ASYNC
> ***************************************
> Comment: Subscriber 1 answers the incoming CSD call.
> ***************************************
> Subscr 1 Send: ATA
> Subscr 1 Receive: ATA
> Subscr 1 Receive:
> Subscr 1 Receive: CONNECT 9600/RLP
> Subscr 2 Receive:
> Subscr 2 Receive: CONNECT 9600/RLP
> ***************************************
> Comment: Subscriber 2 changes from online mode to command mode.
> ***************************************
> Subscr 2 Send: +++
> Subscr 1 Receive: +++
> Subscr 2 Receive:
> Subscr 2 Receive: OK
> ***************************************
> Comment: Subscriber 2 hangs up the CSD call.
> ***************************************
> Subscr 2 Send: ATH
> Subscr 2 Receive: ATH
> Subscr 2 Receive: OK
> Subscr 1 Receive:
> Subscr 1 Receive: +CAUSE: 8:16
> Subscr 1 Receive: NO CARRIER
> Example 3:
> ***************************************
> Comment: CSD call handling - incoming call: Answer CSD call automatically.
> ***************************************
> ***************************************
> Comment: Subscriber 2 makes CSD call to subscriber 1.
> ***************************************
> Subscr 2 Send: ATD00441522400080
> Subscr 2 Receive: ATD00441522400080
> ***************************************
> Comment: Subscriber 1 answers the incoming CSD call after 3 rings automatically.
> ***************************************
> Subscr 1 Receive:
> Subscr 1 Receive: +CRING: REL ASYNC
> Subscr 1 Receive:
> Subscr 1 Receive: +CRING: REL ASYNC
> Subscr 1 Receive:
> Subscr 1 Receive: +CRING: REL ASYNC
> Subscr 2 Receive:
> Subscr 2 Receive: CONNECT 9600/RLP
> Subscr 1 Receive:
> Subscr 1 Receive: CONNECT 9600
> ***************************************
> Comment: Subscriber 1 changes from online mode to command mode.
> ***************************************
> Subscr 1 Send: +++
> Subscr 2 Receive: +++
> Subscr 1 Receive:
> Subscr 1 Receive: OK
> ***************************************
> Comment: Subscriber 1 changes back to online mode.
> ***************************************
> Subscr 1 Send: ATO
> Subscr 1 Receive: ATO
> Subscr 1 Receive: CONNECT 9600
> ***************************************
> Comment: Subscriber 1 change again to command mode.
> ***************************************
> Subscr 1 Send: +++
> Subscr 2 Receive: +++
> Subscr 1 Receive:
> Subscr 1 Receive: OK
> ***************************************
> Comment: Subscriber 1 hangs up the CSD call.
> ***************************************
> Subscr 1 Send: ATH
> Subscr 1 Receive: ATH
> Subscr 1 Receive: OK
> Subscr 2 Receive:
> Subscr 2 Receive: +CAUSE: 8:16
> Subscr 2 Receive: NO CARRIER