Dialogic 6.2 ユーザーズマニュアル

Loop Start Signaling

November 2009

309

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.

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.

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.

 shows how a Brooktrout module processes an incoming 

call received over an FXS loop start trunk.

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_