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Outbound Calls Have Dead Air

Jeremy Boilard

Problem Statement

Some users report that outbound calls from specific extensions result in dead air. No error message is presented, and inbound calls to the affected extensions still work.

Impact

Outbound calling is impaired for a subset of users or extensions, while inbound calling may remain functional. Users may be unable to complete external calls even after rebooting phones or restarting local equipment.

Alarm

No alarm was associated with this issue.

Troubleshooting Steps

  1. Confirm the scope of the issue: identify whether the problem affects one extension, multiple extensions, one site, or all users.
  2. Verify call direction: confirm whether inbound calls, internal extension-to-extension calls, and outbound calls are affected differently.
  3. Reproduce the issue from an affected extension and note whether there is dial tone, ringing, dead air, fast busy, or any display message.
  4. Test from a known-working extension using the same outbound dialing pattern to determine whether the issue follows the user, device, extension, or site.
  5. Confirm the outbound dialing format being used, including any required access prefix, country code, area code, or emergency/local dialing rules.
  6. Check whether the affected extensions have the correct outbound calling permissions, class of service, call restrictions, and caller ID configuration.
  7. Review the PBX or hosted voice platform call logs for the failed outbound attempts. Confirm whether the calls are being routed to the carrier, rejected locally, or failing after carrier handoff.
  8. Check SIP trunk or carrier status for registration, trunk availability, route availability, and any recent maintenance or outage notifications.
  9. If only specific devices are affected, reboot the phone once, verify network connectivity, and confirm the phone has current provisioning and registration status.
  10. If rebooting has already been attempted multiple times without improvement, avoid repeated restarts and escalate with call examples, timestamps, affected extensions, dialed numbers in sanitized form, and call log results.

Resolution

No confirmed root cause or fix was documented in the ticket. Use the troubleshooting steps to isolate whether the failure is caused by extension permissions, dialing pattern, PBX routing, device registration, or carrier/SIP trunk handling. If outbound calls still result in dead air after local configuration and call-log checks, escalate to the voice platform or carrier support team with sanitized call examples and timestamps.