Dialogic 6.2 Ground Start Signaling, FXO Ground Start, Incoming Call Processing, November 289

Ground Start Signaling

Ground Start Signaling

Brooktrout modules support two types of ground start signaling:

„Foreign Exchange - Office (FXO)

„Foreign Exchange - Subscriber (FXS)

When operating in FXO mode, the module assumes the far end of the connection is an FXS termination. When operating in FXS mode, the module assumes the far end is an FXO termination. The timing diagrams on the pages that follow use the labels “FXO” or “FXS” rather than “Rx” or “Tx” for hookswitch states to illustrate this point.

FXO Ground Start

To configure a Brooktrout module for FXO ground start signaling, the host must issue an L4L3mENABLE_B_CHANNEL with an IISDN_ROBBED_BIT_DATA structure that contains the following settings:

„in_trunk_type = IISDNttFXO_GDSTART

„out_trunk_type = IISDNttFXO_GDSTART

„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.

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 ring ground at the far end (FXS end). The module then collects dial pulse digits from the network; the maximum number of digits the module expects to receive must be specified in the max_incoming_digit_ count field. The digits are reported to the host in an L3L4mSETUP_ IND message. To answer the call, the host must issue an L4L3mCONNECT_REQUEST message.

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