Analog FXO Trunk Settings

This topic describes all the settings on an FXO trunk for reference.

Basic settings

Setting Description
Name Give this trunk a name to help you identify it.
RX Volume Set the receiving volume of the FXO port.
TX Volume Set the transmitting volume of the FXO port.

Advanced settings

The advanced settings require professional knowledge of analog telephony, carefully configure the advanced settings, or the trunk would not work. For different PSTN providers, you may need to adjust the advanced settings to suit your situation.

The following settings are included on the Advanced page.

Hangup Detection
Hangup Detection settings help the PBX to detect if a call is hung up. If you find outbound calls through the FXO trunk cannot be disconnected, adjust the Hangup Detection settings.
Setting Description
Hangup Detection Method

Select the Hangup Detection method:

  • Busy Tone: The call will be disconnected if a busy tone is detected by the Yeastar P-Series PBX System.

  • Polarity Reversal: The call will be disconnected if a polarity reversal is detected by the Yeastar P-Series PBX System.

  • Loop Current Disconnect: When the remote side of FXO trunk disconnects the call and creates a loop current, Yeastar P-Series PBX System will detect the loop current and disconnect the call.

Busy Count Specify how many busy tones to wait for before disconnecting.

The default value is 4.

Note: PBX may fail to detect the busy tone if the value of Busy Count is too high.
Busy Pattern Specify the cadence of busy signal.
  • Format: {sound},{silence}.

    For example, 500,500 means 500ms on, 500ms off.

  • If you select [None], the system will accept any regular sound-silence pattern that repeats Busy Count times as a busy signal.
  • If you select a busy tone, the system will further check the length of the tone and silence, which will further reduce the chance of a false positive disconnection.
Busy Interval (s) The busy detection interval.
Frequency Detection Enable or disable detection of busy signal frequency.
Busy Frequency If the Frequency Detection is enabled, you need to specify the local frequency.
Answer Detection
Setting Description
Answer Detection Method

Specify the method to detect if a call is answered. This setting affects the accuracy of call duration tracking.

  • [None]: PBX will start counting call duration after you use the FXO trunk to call out, whether the call is answered or not.

  • Polarity Reversal: If this option is selected, PBX will start counting call duration after a polarity signal is detected.

    Note: Before you select this option, contact the PSTN provider to check if they supports polarity.
Caller ID Settings
Caller ID Settings helps the system to detect Caller ID. If an incoming PSTN call does not display Caller ID, you need to confirm with your service provider if the line has enabled Caller ID feature. If this line does support Caller ID, configure these settings to solve this problem.
Setting Description
Caller ID Detection Enable or disable Caller ID detection.
Caller ID Detection Mode

Define the start of a Caller ID signal.

  • After Ringing: Detect Caller ID after first ringing.

  • After Polarity: Detect Caller ID after polarity reversal.

  • Before Ringing: Detect Caller ID before first ringing.

Caller ID Signaling

Specify the type of caller ID signaling to use according to the direction provided by your service provider.

  • Bell202

  • V23-Japan

  • DTMF
  • ETSI-V23
Other Settings
Setting Description
Ringing Detection Timeout (ms) FXO (FXS signalled) devices must have a timeout to determine if there was a hangup before the line was answered.
  • Valid value: 1000-10000
  • Default value: 5000
Echo Cancellation Enable or disable echo cancellation.

DID Name

DID Name is used to identify which telephone number was dialed. When an inbound call reaches the trunk, the name will be displayed on the called party's device.
Inbound to Outbound Number This setting is typically for Inbound Route to Outbound Route feature.

If you wish the inbound call through this trunk to be redirected via an outbound route, enter the destination number in this field.

Inbound Caller ID Reformatting

When a user calls in the PBX, the trunk provider may send a caller ID that is inconvenient for you to redial directly.

In this case, you can reformat inbound caller ID based on a trunk. The caller ID will be reformatted before it is sent to the called party.

For more information, see Reformat Inbound Caller ID based on a Trunk.