3Com VCX v7111 User Manual page 257

One -stage dialing incorporates the following FXO functionality:
Waiting for Dial Tone
The Waiting for Dial Tone feature enables the gateway to dial the digits to the Tel side
only after detecting a dial tone from the PBX line. The ini file parameter
IsWaitForDialTone is used to configure this operation.
Time to Wait Before Dialing
The Time to Wait Before Waiting feature defines the time (in msec) between seizing the
FXO line and starting to dial the digits. The ini file parameter WaitForDialTime is used to
configure this operation.
The ini file parameter IsWaitForDialTone must be disabled for this mode.
Answer Supervision
The Answer Supervision feature enables the FXO gateway to determine when a call is
connected, by using one of the following methods:
Polarity Reversal: the gateway sends a 200 OK in response to an INVITE only when
it detects a polarity reversal.
Voice Detection: the gateway sends a 200 OK in response to an INVITE only when it
detects the start of speech (or ringback tone) from the Tel side.
Two-Stage Dialing
Two-stage dialing is when the IP caller is required to dial twice. The caller initially dials to the
FXO gateway, and only after receiving a dial tone from the PBX (via the FXO gateway), dials
the destination telephone number.
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3Com VCX V7111 VoIP Gateway User Guide
257