The CLS (class of service) CFHA (call forward and hunt override allowed), when allocated to an extension TN allows that particular extension user to dial a FFC (flexible feature code) followed by an extension number. The called extension will ring even if call forward is set or if ringing and not answered will continue to ring instead of following the forward no answer treatment, if the called extension is already on a call, busy tone will be returned instead of the call receiving the hunt treatment.
Obviously this feature should not be offered to every extension user, as in most cases the extensions are programmed up to direct calls appropriately therefore care should be taken before giving this service to an extension TN as it will allow the person using the extension to call, directly, members of senior management even though they have decided to re-direct their calls.
The FFC for the feature can be found in LD 57 the mnemonic is CFHO (call forward and hunt override).