User`s manual
MP-1xx H.323
MP-1xx H.323 User’s Manual 158 Document #: LTRT-65104
8.6 Call Termination on MP-1xx FXO
The following five methods for call termination are supported by the MP-1xx/FXO. Note that the
disconnection methods used by the MP-1xx must be supported by the CO or PBX.
• Detection of polarity reversal / current disconnect -
This is the recommended method. The call is immediately disconnected after polarity
reversal or current disconnect is detected on the Tel side (assuming the PBX / CO produces
this signal).
Relevant ini file parameters: EnableReversalPolarity, EnableCurrentDisconnect,
CurrentDisconnectDuration, CurrentDisconnectDefaultThreshold and
TimeToSampleAnalogLineVoltage.
• Detection of Reorder / Busy tones -
The call is immediately disconnected after Reorder / Busy tone is detected on the Tel side
(assuming the PBX / CO produces this tone). This method requires the correct tone
frequencies and cadence to be defined in the Call Progress Tones file. If these frequencies
are not known, define them in the CPT file (the tone produced by the PBX / CO must be
recorded and its frequencies analyzed). This method is slightly less reliable than the previous
one. You can use the CPTWizaed (described in Section
F.1.3 on page 220) to analyze Call
Progress Tones generated by any PBX or telephone network.
Relevant ini file parameters: TimeForReorderTone.
• Detection of silence -
The call is disconnected after silence is detected on both call directions for a specific
(configurable) amount of time. The call isn’t disconnected immediately; therefore, this method
should only be used as a backup.
Relevant ini file parameters: EnableSilenceDisconnect and FarEndDisconnectSilencePeriod
(with DSP templates number 2 or 3).
• Interruption of RTP stream -
Relevant ini file parameters: BrokenConnectionEventTimeout and
DisconnectOnBrokenConnection. Note that this method operates correctly only if silence
suppression is not used.
• Protocol-based termination of the call from the IP side.
8.7 Mapping PSTN Release Cause to H.323 Response
The MP-1xx FXO gateway is used to interoperate between the H.323 network and the
PSTN/PBX. This interoperability includes the mapping of PSTN/PBX Call Progress Tones to
H.323 Release Causes for IPTel calls. The converse is also true: For TelIP calls, the H.323
Release Causes are mapped to tones played to the PSTN/PBX.
When establishing an IPTel call the following rules are applied:
If the remote party (PSTN/PBX) is busy and the FXO gateway detects a Busy tone, it sends a
Release Cause with User Busy (17) to IP. If it detects a Reorder tone, it sends a Release Cause
with No Route to Destination (3) to IP. In both cases the call is released. Note that if
‘DisconnectOnBusyTone = 0’ the FXO gateway ignores the detection of Busy/Reorder tones and
doesn’t release the call.
For all other MP-1xx FXO releases (caused when there are no free channels in the specific hunt
group, or when an appropriate rule for routing the call to a hunt group doesn’t exist), the MP-1xx
sends H.323 response (to IP) according to the parameter ‘DefaultReleaseCause’. This parameter
defines Q.931 release causes. Its default value is ‘3’, that is mapped to H.323 Release Cause
with No Route to Destination. By changing its value to ‘34’ No Circuit Available response is sent.
Other causes can be used as well.