User`s manual

Version 5.6 327 November 2008
SIP User's Manual 7. IP Telephony Capabilities
7.4.1.1 One-Stage Dialing
One-stage dialing is when the FXO device receives an IP-to-Tel call, off-hooks the PBX line
connected to the telephone, and then immediately dials the destination telephone number.
In other words, the IP caller doesn't dial the PSTN number upon hearing a dial tone.
Figure 7-2: Call Flow for One-Stage Dialing
One-stage dialing incorporates the following FXO functionality:
 Waiting for Dial Tone: Enables the device 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: 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.
Note: The ini file parameter IsWaitForDialTone must be disabled for this mode.
 Answer Supervision: The Answer Supervision feature enables the FXO device to
determine when a call is connected, by using one of the following methods:
• Polarity Reversal: device sends a 200 OK in response to an INVITE only when it
detects a polarity reversal.
• Voice Detection: device sends a 200 OK in response to an INVITE only when it
detects the start of speech (or ringback tone) from the Tel side. (Note that the IPM
detectors must be enabled).