# PSTN trunk settings reference

This reference describes the fields available when creating or editing an
inbound PSTN trunk. The settings are grouped by the tabs shown in the DIDWW
User Panel.

For configuration steps, see [Create a PSTN trunk](how-to-guides/create-pstn-trunk.html) or [Manage PSTN
trunks](how-to-guides/manage-pstn-trunks.html).

## General

The **General** tab identifies the trunk, defines its PSTN destination, and
controls call capacity and ringing timeout.

| Field | Availability | Description |
| --- | --- | --- |
| Name | Required | Unique name used to identify the trunk in the DIDWW User Panel. |
| PSTN Phone Number | Required | Destination to which DIDWW forwards calls. Enter the country code, area code, and subscriber number in E.164 format without `+`. For example, `12065550100`. The destination must be available for PSTN termination. |
| Capacity Limit | Optional | Maximum number of simultaneous calls that DIDWW can deliver through the trunk. This can restrict, but cannot increase, the [Capacity](../../../phone-numbers/capacity/how-capacity-works.html) assigned to a DID number. When the limit is reached, DIDWW attempts another trunk in the same Trunk Group when available. If no other trunk is available, the call is rejected and appears in [Inbound Call Logs](../../../logs-analytics/call-logs/inbound-logs.html#inbound-cdr-logs) with the response `480 Capacity limit for trunk exceeded`. Enter a value from 1 to 32767. The default value is **Unlimited**. |
| Ringing Timeout | Optional | Time DIDWW waits for `200 OK` after an `18x` response. When the timeout is exceeded, the routing attempt ends with the **Ringing timeout** disconnect code. Enter a value from 1 to 32 seconds. |

Use **Check Rate** to confirm that the destination is available and display
its current per-minute rate. Rates vary by destination. See [DIDWW
pricelists](../../../phone-numbers/buy-numbers/download-pricelists.html#services-coverage-pricing-access-pricelists).

## Number Translations

The **Number Translations** tab filters incoming calls by caller ID.

| Field | Availability | Description |
| --- | --- | --- |
| CLI Number List | Optional | [Number List](../number-lists/index.html) used to allow or reject calls by full-number match, prefix match, or length. |

## Trunk Group

This optional tab places the trunk in one [Trunk Group](../trunk-groups/index.html) for failover or load balancing.

| Field | Availability | Description |
| --- | --- | --- |
| Trunk Group | Optional | Group to which the trunk belongs. A trunk can belong to only one group. |
| Priority | Trunk Group selected | Attempt order. Lower values are attempted first. Trunks with the same priority are selected according to **Weight**. Enter a value from 0 to 65535. The default value is `1`. |
| Weight | Trunk Group selected | Relative selection weight among trunks with the same priority. Higher values increase selection likelihood. Enter a value from 0 to 65535. The default value is `65535`. See [**RFC 2782**](https://datatracker.ietf.org/doc/html/rfc2782.html). |

## Related resources

- [Create a PSTN trunk](how-to-guides/create-pstn-trunk.html) - Create a
  trunk and configure the settings described on this page.
- [Manage PSTN trunks](how-to-guides/manage-pstn-trunks.html) - View, edit,
  or delete an existing trunk.
- [PSTN trunks](index.html) - Understand how DIDWW forwards inbound calls to
  PSTN destinations.
- [Assign a voice trunk](../../../phone-numbers/my-numbers/how-to-guides/assign-voice-trunk.html#user-panel-assign-trunk) - Assign the trunk to
  one or more DID numbers.
- [Trunk Groups](../trunk-groups/index.html) - Configure failover and load
  balancing across multiple trunks.

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