Troubleshooting Guide 48 Document #: LTRT-57601
MediaPack, Mediant 1000, Mediant 2000
Table 7-1: Unterminated PBX FXO Call Troubleshooting
Possible Cause Solution
1.
The device is not correctly
configured to identify the
disconnection signaling used by
the PBX.
The following disconnection methods are supported:
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 parameters: EnableReversalPolarity,
EnableCurrentDisconnect, CurrentDisconnectDuration,
CurrentDisconnectDefaultThreshold, and
TimeToSampleAnalogLineVoltage.
Detection of Reorder / Busy / Dial tones: The call is
immediately disconnected after Reorder / Busy / Dial
tone is detected on the Tel side (assuming the PBX / CO
generates this tone). This method requires that the
correct tone frequencies and cadence are defined in the
Call Progress Tones (CPT) file. If these frequencies are
unknown, you can detect them using the procedure
described below and configure them in the CPT file. This
method is slightly less reliable than the previous one.
Relevant parameters: DisconnectOnBusyTone and
DisconnectOnDialTone.
A special DTMF code: A digit pattern that when
received from the Tel side, indicates to the device to
disconnect the call.
Relevant parameter: TelDisconnectCode.
Detection of silence: The call is disconnected after
silence is detected on both call directions for a user-
defined time. The call isn’t disconnected immediately;
therefore, this method should only be used as a backup
mode.
Relevant parameters: EnableSilenceDisconnect and
FarEndDisconnectSilencePeriod.
To detect the frequency and cadence of reorder/busy tones sent by a PBX, you can
perform one of the following:
Create a new CPT file, using the CPTwizard (refer to ''CPTWizard'' on page 77).
Identify the busy or re-order tones used by the PBX - refer to the procedure below.
¾ To detect the frequency and cadence of the reorder or busy tones
sent by the PBX:
1. Make a call (using G.711) between the FXO device, which is connected to the PBX,
and a remote entity in the IP network.
2. Capture the call using a network sniffer such as Wireshark (refer to ''Wireshark
Network Sniffer'' on page 69).
3. Disconnect the call from the PBX side, and then wait approximately 30 seconds before
stopping the Wireshark recording.
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