Tuesday, January 29, 2013

Case Study: Cisco Phone 7942 unexpected auto-call/auto-dial

Problem Description:
This is an actual ticket escalated to our team.

User reported that his Cisco IP Phone automatically dials a number once he picks up the handset of the phone.

HW/SW Versions:
  • Cisco IP Phone 7942
  • SCCP42.9-2-3S
  • CUCM 7.1 (
  • Same behavior is observed when pressing the speaker button;
  • Same behavior is observed when pressing the headset button;
  • Only one number is being called consistently;
  • IP Phone is registered correctly in CUCM;
  • Resetting the phone has stopped the auto-dialling.

Root Cause:
After some research, we found the bug documenting this behavior:

CSCtz29414 - 7942/7962 - Call History is Auto-Dialed When Pressing Speaker Button

When a 7942/62 phone is populated with call history records (e.g. received/placed/missed calls), the endpoint will auto-dial the number contained in its call history when the speaker button is pressed.

IP Phone Call History contains Received/Placed/Missed Phone number record prior to pressing speaker button to go off-hook. Phone will continue to auto-dial the number listed in Call History once error condition is experienced.

Reset IP Phone to clear error condition

1st Found-In:


As per the bug above, reset the phone

Permanent Fix:
Upgrade the phone firmware.

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