PSTN Trunk Settings

When you configure a PSTN trunk, you may need to configure some of the advanced settings. This reference describes all the settings on a PSTN trunk.

Basic Settings

Navigation path: Settings > PBX > Trunks, edit a trunk on the Basic tab.

Settings 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.
Enable SLA After enabling SLA, users can share this trunk to make outbound calls and receive inbound calls by BLF keys on their phones. In this way, Inbound Route settings and Outbound Route settings for the trunk is invalid.
Allow Barge Whether or not other stations are allowed to join a call which is in progress on this trunk by pressing the same line button.
Hold Access The hold option specifies hold permissions for this trunk.
  • Open: any station can place this trunk on hold and other station is allowed to resume the call on hold.
  • Private: only the station that has placed the trunk on hold is allowed to resume the call.
Failover Destination Route the call if no one answer this call.

Hangup Detection Settings

Hangup Detection settings help the PBX to detect if a call is hung up. If you find the PSTN call could not be disconnected, adjust the Hangup Detection settings.

Navigation path: Settings > PBX > Trunks, edit a trunk on the Advanced tab.

Settings Description
Hangup Detection Method

Choose the Hangup Detection Type:

  • Busy Tone (Default): The call will be disconnected if a busy tone is detected by the Yeastar S-Series VoIP PBX.

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

  • Loop Current Disconnect: When the remote side of PSTN trunk disconnects the call and creates a loop current, will detect the loop current and disconnect the call.
Busy Count Specify how many busy tones to wait for before disconnecting.

The default is 4. It is better to set it to 6 or 8.

Note: PBX may fail to detect the busy tone if the value of Busy Count is too high.
Busy Pattern Set the cadence of your busy signal if Hangup Detection Method is set to Busy Tone (Default). In most countries, the cadence of your busy signal is set to 500ms on and 500ms off.

  • If you choose None, the PBX will accept any regular sound-silence pattern that repeats Busy Count times as a busy signal.

  • If you choose a busy pattern, the system will further check the length of the tone and silence, which will further reduce the chance of a false positive disconnection.

The format is {Sound},{Silence}. e.g. 500,500 means 500ms on, 500ms off.
Busy Interval The busy detection interval.
Frequency Detection Used for Frequency Detection (Enable detecting the busy signal frequency or not).
Busy Frequency If the Frequency Detection is enabled, you need to specify the local frequency.

Answer Detect Type Settings

Navigation path: Settings > PBX > Trunks, edit a trunk on the Advanced tab.

Settings Description
Answer Detection Method Answer Detection will help the system to accurately bill your calls.

  • Default: PBX will start to charge once you grab the PSTN trunk to call out, whether the call is answered or not.

  • Polarity Detection: If the PSTN trunk supports polarity, you can choose Polarity Detection. When the callee answers the call, the provider will send a polarity signal, and then the system starts to bill.
DID Number If you wish the inbound call through this trunk to be redirected via outbound route, please fill in the destination number to be called.

Caller ID Settings

Caller ID Settings will help 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.

Navigation path: Settings > PBX > Trunks, edit a trunk on the Advanced tab.

Settings Description
Caller ID Detection Enable/Disable the Caller ID detection.
Caller ID Start

This option allows you to define the start of a Caller ID signal.

  • Ring: start when a ring is received (Caller ID Signaling: Bell_USA, DTMF).

  • Polarity: start when a polarity reversal is started (Caller ID Signaling: V23_UK, V23_JP, DTMF).

  • Before Ring: start before a ring is received (Caller ID Signaling: DTMF).
Caller ID Signaling

This option defines the type of Caller ID signaling to use. It can be set to one of the following:

  • Bell: bell202 as used in the United States

  • v23_UK: suitable in the UK

  • v23_Japan: suitable in Japan

Other Settings

Navigation path: Settings > PBX > Trunks, edit a trunk on the Advanced tab.

Settings Description
Ring Detect Timeout (ms) FXO (FXS signalled) devices must have a timeout to determine if there was a hangup before the line was answered. Rang from 1000 to 8000. Default: 8000.
Echo Cancellation Enable or disable echo cancellation.
Release Trunk Release the trunk, and hang up all the calls on this trunk.
DNIS

DNIS Name

 DNIS (Dialed Number Identification Service) is a telephone service that identifies for the receiver of a call the number that the caller dialed. If you want to use the feature, enable it and fill in the DNIS name.

Adapt Caller ID

The incoming caller ID that matches the adaptation pattern will be adapted, so that you can press the call record directly on your phone call back a number.

For more information, see Change Inbound Caller ID.

Navigation path: Settings > PBX > Trunks, edit a trunk on the Adapt Caller ID tab.

Settings Description
Patterns The following characters have special meanings:
  • X matches the numbers 0- 9;
  • Z matches the numbers 1-9;
  • N matches the numbers 2- 9;

  • [12345-9] matches the numbers in the bracket (in this example, 1, 2, 3, 4,5, 6, 7, 8,

    9);

  • Wildcard matches one or more numbers. E.g. "9011." matches anything starting with 9011 (excluding 9011 itself);

  • Wildcard "!" matches none or more than one numbers. E.g. "9011T matches anything starting with 9011 (including 9011 itself);
Strip Strip allows you to specify the number of digits that will be stripped from the front of the Caller ID before the call is displayed. For example, if the incoming Caller ID is 05929999999, but you need to dial number 5929999999 to call back, one digit should be stripped.
Prepend These digits will be prepended to the Caller ID before the call is displayed. For example, if the incoming caller ID is 5929999999, but you need to dial digit 0 before the number to call back, 0 should be prepended.