Investigate CUCM DTMF negotiation when intercom audio works but unlocking fails

Preserve working video while a voice administrator checks the documented DTMF mismatch and SIP-profile remedy.

Source facts

Verkada documents a Cisco Unified CM fault in which intercom video and audio work but keypad unlocking fails. The guide attributes the example to a DTMF payload mismatch: Cisco phones often use 101 while the intercom negotiates 121. It warns that enabling Media Termination Point can resolve the DTMF mismatch while breaking video. The documented remedy instead keeps MTP off on both devices and applies the specified SIP profile to the phone and intercom in CUCM.

Source: Verkada Help — SIP Integration: Cisco Unified CM.

Applicability

Applies to the CUCM integration and fault described by Verkada. These payload values are a documented diagnostic example, not proof of what a particular site has negotiated.

DSE recommendation

DSE recommends collecting the exact failing call behavior before changing media resources. Have the voice administrator inspect the relevant SIP profile and negotiated DTMF settings for both ends. Preserve the working video configuration and make a reversible change in an approved window. Use the vendor’s actual illustrated profile rather than guessing settings from the symptom. Keep door unlocking under an authorized test procedure so diagnosing signaling does not create unattended entry.

Verification

Repeat the same approved call before and after the change and score video, two-way audio, and the unlock key separately. Confirm the correct door response with an observer. If the failure persists, retain the configuration comparison and relevant call evidence for Support rather than repeatedly enabling MTP without a defined test.

Official reference

Verkada Help — SIP Integration: Cisco Unified CM. Reviewed October 15, 2026.