• 2.1.1.  Inbound Analog Calls
• 2.1.2.  Outbound Analog Calls

2.1.  Analog Telephone Calls

For each analog loop start channel, the gc_OpenEx( ) function is used to open the voice line device and the telephone network interface device (interface to the loop start telephone line or trunk).

For Springware platforms, the gc_LoadDxParm( ) function is invoked to set voice parameters to be used for the voice channel associated with a line device. These voice parameters are specified in a user-created voice channel parameter (.vcp) ASCII text file. Parameters that are not specified will be assigned their default value automatically. The voice channel parameters include all channel-level parameters set by the voice function, dx_setparm( ), and all enhanced call analysis parameters defined in the voice DX_CAP data structure. This feature is not currently available on DM3 platforms.

2.1.1.  Inbound Analog Calls

For inbound calls, after the operations described in Section 2.1.  Analog Telephone Calls complete, a gc_WaitCall( ) function is issued and waits for an inbound call request on the loop start network interface device.

• When the gc_WaitCall( ) function is issued synchronously, the function waits for the number of rings defined by the default number of rings parameter (set by the .cdp file-not available on DM3, as calls are offered to the application as soon as the firmware has all of the information needed to present the call) or for time-out to expire. When either condition occurs, the function returns.
• When the gc_WaitCall( ) function is issued asynchronously, the function completes when an unsolicited GCEV_OFFERED event occurs.

When an inbound call is received, the gc_AnswerCall( ) function establishes the conditions for answering the call, answers the call, and continues to monitor for a disconnect. The rings parameter of the gc_AnswerCall( ) function is not used, as the analog protocol does not generate the actual ringback; it is generated by the analog switch.

During the call, Global Call continually tests for call disconnect by monitoring for disconnect tones or for a loop current change.

The gc_CallAck( ) function is not supported for analog calls.

2.1.2.  Outbound Analog Calls

For an outbound call, after the operations described in Section 2.1.  Analog Telephone Calls complete, the gc_MakeCall( ) function is invoked to make an outgoing call using the specified loop start network and voice resources. First, the channel used to make the outbound call is taken off-hook. Then the number is dialed using DTMF signaling, MF tone signaling, or pulse dialing. (Pulse dialing is not available on DM3 boards.) Call progress tones are monitored to track the progress (current status) of the call. Enhanced call analysis is used for outbound analog telephone calls.

On Springware boards, the call progress tones can be changed from their default values by using the dx_ API to change the appropriate default tones in the firmware. (Refer to the Voice API Library Reference.) Other call analysis parameters can be set by the gc_LoadDxParm( ) function (Springware only). Global Call analog technology can be configured to not use call progress tones, but the protocol will transition to the connected state immediately after dialing, as there is no way for the protocol to determine connection status with call progress analysis.

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