User`s manual

SIP User's Manual 408 Document #: LTRT-83303
Mediant 1000 & Mediant 600
7.3.1.2 Two-Stage Dialing
Two-stage dialing is when the IP caller is required to dial twice. The caller initially dials to
the FXO device and only after receiving a dial tone from the PBX (via the FXO device),
dials the destination telephone number.
Figure 7-2: Call Flow for Two-Stage Dialing
Two-stage dialing implements the Dialing Time feature. Dialing Time allows you to define
the time that each digit can be separately dialed. By default, the overall dialing time per
digit is 200 msec. The longer the telephone number, the greater the dialing time.
The relevant parameters for configuring Dialing Time include the following:
 DTMFDigitLength (100 msec): time for generating DTMF tones to the PSTN (PBX)
side
 DTMFInterDigitInterval (100 msec): time between generated DTMF digits to PSTN
(PBX) side
7.3.1.3 Call Termination (Disconnect Supervision) on FXO Devices
The FXO Disconnect Supervision enables the device's FXO ports to monitor call-progress
tones from a PBX or from the PSTN. This allows the FXO to determine when the call has
terminated on the PBX side, and thereby, prevents analog trunks (i.e., lines to the PBX)
from getting “stuck” when the called phone hangs up.
The PBX doesn't disconnect the call, but instead signals to the device that the call is
disconnected using one of the following methods:
 Detection of polarity reversal / current disconnect: The call is immediately
disconnected after polarity reversal or current disconnect is detected on the Tel side
(assuming the PBX / CO produces this signal). This is the recommended method.