Dialogic 6.2 manual FXS Loop Start, November 309

Loop Start Signaling

FXS Loop Start

To configure a Brooktrout module for FXS loop start signaling, the host must issue an L4L3mENABLE_CAS with an IISDN_ROBBED_ BIT_DATA structure that contains the following settings:

„in_trunk_type = IISDNtt5ESS_LPSTART

„out_trunk_type = IISDNtt5ESS_LPSTART

„max_incoming_digit_count = 0 (no digits collected)

„timed_answer_supervision = 1 (timer expiration indicates far end answer)

„fgb_fgd_mode = 0 (not used)

The remaining settings are described in the context of incoming and outgoing calls in the subsections that follow.

Note: The FXO end of a loop start connection uses the same A and B bit values for both idle and connected states. Because of this, the Brooktrout module cannot detect when the FXO end goes on hook. To idle the channel, the host must detect the lack of data coming from the FXO end and issue an L4L3mCLEAR_ REQUEST to disconnect the call. To ensure the FXO end returns to an idle state, the host must also reset the channel by issuing an L4L3mDISABLE_CAS immediately followed by an L4L3mENABLE_CAS in order to make another call.

Incoming Call Processing

During an incoming call, the host receives an L3L4mPRE_SEIZE message if send_preseize_event = 1 in the IISDN_ROBBED_BIT_ DATA structure. This message is sent when the module detects ringing from the far end (FXO end). No digits are collected in FXS loop start mode; to answer the call, the host must issue an L4L3mCONNECT_REQUEST message.

Figure 43 shows how a Brooktrout module processes an incoming call received over an FXS loop start trunk.

Outgoing Call Processing

During an outgoing call, the host receives an L3L4mPROGRESS in response to the L4L3mCALL_REQUEST to start the call. The host then receives an L3L4mSEIZE_COMP message if send_seize_comp_

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