Digital Phone DTMF Sometimes Fail on Calls

Products Affected: All Versions of Wave IP, Digital Phones


Using a Wave IP digital phone for a call, DTMF does not register on an external auto-attendant.


Some auto-attendants require longer than 80 ms DTMF (which is our standard). LIne conditions can also affect this.


DTMF intermittently fails when using digital phones.


  1. Access registery editor (see Edit the Windows Registry).
  2. Add a new registry DWORD at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Cpm\Parameters.
    • Parameter Name: MinimumDTMF

    • Parameter Type: DWORD

    • Parameter Value: 120

  3. Close registry editor.
  4. Identify an appropriate service window and restart Wave to apply the change.