The Do Not Disturb (DND) feature allows phone users to disable audible ringing for incoming calls. When DND is enabled, incoming calls do not ring on the phone, however there is visual alerting and the call information displays, and a call can be answered if desired. When a local IP phone calls another local IP phone that is in the DND state, the message “Ring out DND” displays on the calling phone indicating that the target phone is in the DND state.

Phone users can toggle DND on and off by using the DND softkey in the idle or ringing call states. A SSCP phone user can toggle DND on or off in the ringing state only if DND in not already active on the phone. If DND is already active when a new call comes in, the SCCP phone user cannot change the DND state by pressing the DND softkey.

If an SSCP phone user toggles DND on during an incoming call, the DND state remains active for the current call only. If a SIP phone user toggles DND on during an incoming call, the DND state remains active during the current call and for all future calls until the user explicitly toggles DND off.

Pressing the DND softkey during an incoming call forwards the call to the call-forward no answer destination if Call Forward No Answer is enabled. If Call Forward is not enabled, pressing the DND softkey disables audible ringing and visual alerting, but the call information is visible on the phone display.

In Cisco CME 3.2.1 and later versions, DND can be blocked from phones with the feature-ring function. A feature ring is a triple-pulse ring, a type of ring cadence in addition to internal call and external call ring cadences. For example, an internal call in the United States rings for 2 seconds on and 4 seconds off (single-pulse ring), and an external call rings for 0.4 seconds on, 0.2 seconds off, 0.4 seconds on, and 0.2 seconds off (double-pulse ring).

The triple-pulse ring is used as an audio identifier for phone users. For example, each salesperson in a sales department could have an IP phone with a button sharing the same set of ephone-dns with the sales staff and another button for their private line for preferred customers. To help a salesperson identify an incoming call to his or her private line, the private line can be configured with the feature-ring function. You can disable the DND function on feature-ring lines. In the preceding example, salespeople could activate DND on their phones and still hear calls to their private lines.

In Cisco Unified CME 7.1 and later versions, the Do Not Disturb (DND) feature for SIP phones prevents incoming calls from audibly ringing a phone. When DND is enabled, the phone flashes an alert to visually indicate an incoming call instead of ringing and the call can be answered if desired. The message “Do Not Disturb is active” displays on the phone and calls are logged to the Missed Calls directory.

In versions earlier than Cisco Unified CME 7.1, the DND feature blocks incoming calls to a SIP phone with a busy tone. Cisco Unified CME rejects calls to all lines on the phone and plays a busy tone to the caller. Received calls are not logged to the Missed Calls directory on the phone.

DND applies to all lines on the phone. If DND and Call Forward All are both enabled on a phone, Call Forward All takes precedence on incoming calls.

You must enable DND for a SIP phone through Cisco Unified CME. The DND softkey displays by default on supported SIP phones in both the Ringing and idle states. You can remove or change the order of this softkey using a voice register template.

A phone user can toggle DND on and off at the phone by using the DND softkey. If a SIP phone user activates DND during an incoming call, the DND state remains active during the current call and for all future calls until the user explicitly toggles DND off.

If a phone user toggles DND on or off at the phone, Cisco Unified CME restores the DND state after the phone resets or restarts, if you save the running configuration before Cisco Unified CME reboots.

For configuration information, see Configure Do Not Disturb on SIP Phones.

Table 1 compares the DND configuration for SIP phones with different phone load versions: