Thursday, August 9, 2012

CME Call Park

Basic Call Park

This feature is used to hold an active call in a temporary park slot in order to retrieve it later using the same phone or different phone. This is different than call-hold/resume feature which is achieved using hold softkey.

CME 7.1 adds Call Park support for SIP phones as well. Therefore a call parked by SCCP phone can be retrieved from a SIP phone and vice versa.

There are different ways to park and retrieve calls which we will cover later.

You create park slot(s) using ephone-dn command and by setting the ephone-dn to operate in park-slot mode. Once the call is parked, the parking slot DN will be displayed on top of the phone's screen. This DN will be used later to retrieve the call.

Note: Each slot can hold one call at a time

Callers for a parked call will hear CME system's music on hold if they are using G711 or G729 with XCODER. Note that the park softkey is displayed in connected state only if you have created at least one park slot for your Cisco CME system

Park slots can be monitored using button m command on SCCP phones only. This will add a "status" button to the phone which will show in-use when the slot is occupied.

You can create multiple park slots with same extension (shared lines). For example, IT department users know that all calls parked in slot 3001 is directed to them. When retrieving calls from the shared park slots, they will follow FIFO model. To get this working, a couple of prerequisites should be fulfilled:

  1. Each ephone-dn should have no huntstop except the last DN.
  2. Each ephone-dn must be configured with preference command.

Optionally, you can enabling notifications to be sent to extension which parked the call. This is required in case the call is parked and not retrieved. This is enabled using two commands which are timeout and limit.  For example, if you configured timeout as 30 and limit as 20, a reminder ring will be sent to the extension which parked the call every 30 seconds for 20 times. As soon as the maximum number of reminders has been sent (after 20 * 30 = 600 seconds [10 minutes]), the call in the park slot is disconnected.

Note: If the timeout keyword is not used, no reminder ring is sent to the extension that parked the call

You can also specify another extension to receive a reminder ring using notify keyword. In this case the initiator of the call park as well as the notify extension will receive the reminder ring.

Also, in case timeout/limit are exceeded you can configure CME to revert the call back to initiator using recall command or transfer it to another user using the command transfer.

How CME Selects a Free Slot to Park the Call?

When you initiate call park, the call is transferred to a park slot that has the same last two digits as the extension. For example, if you are using extension 312 and you parked a call from that extension, the call is parked in a park slot with a number ending in 12 if available. Assuming you created park slots with numbers 711, 712, 713, and 714, a call parked from extension 312 uses park slot 712 if possible. If not available, any available park slot is used randomly.

Directed Call Park
This differs from basic call park in away that you can park the call in specific park slot rather than keeping the selection of park slot to CME.

Park Reservation Groups
In this method a group of park slots will be reserved to be used with a group of phones. This isn't supported for directed park slots. A park slot configured with a park reservation group can only be used by phones configured with the same park reservation group.

To be more clear, phones within a group can park to slots within the same group only. However, any phone in CME (whether within the group or not) can retrieve any parked call. Therefore, reservation groups is applicable for call parking but not retrieval.

Dedicated Call Park Slots

A dedicated, private call-park slot can be configured for an ephone using the reserved-for keyword in the park-slot command. The dedicated call-park slot is associated with the primary extension of the ephone. All extensions on this phone can park calls in the dedicated park slot.

Note: In case dedicated slot isn't available, CME uses standard call park procedure

How to park and retrieve calls?
1. You must enable the call-park system application command.
2. SCCP phones support the Pickup soft key for Park Retrieval only if the service directed-pickup command is configured (default). Otherwise, the Pickup soft key initiates Local Group Pickup.
3. In case button m is used, you can use the button directly to retrieve the parked call
4. You can block the usage of Transfer softkey in order to initiate call park using the command transfer-park blocked. One exception is dedicated call park which won't be affected by this command
5. Remote phones can park calls using any method (basic, directed, dedicated, etc), but retrieval should be from local phone in the same CME of park slot

Call-Park Redirect

By default call parks over H323/SIP trunks are using hairpin in order to complete. This default behavior can be changed to use H450 or SIP REFER using the command call-park system redirect.

Configuration Template

 call-park system {application | redirect}
 fac {standard | custom dpark-retrieval custom-fac}
ephone-dn dn-tag
 number number
 park-slot [directed] [reservation-group group-number] [reserved-for extension-number] [[timeout seconds limit count] [notify extension-number [only]] [recall] [transfer extension-number] [alternate extension-number] [retry seconds limit count]]
ephone phone-tag
 park reservation-group group-number
voice register pool phone-tag
 park reservation-group group-number


  1. Hi,

    Is CME Call Park feature uses DSP resources e.g. MTP for network hold?


    1. It depends. If you are using simple call park (same codec between CME MoH and phones), then no DSPs since MoH will be streamed from CME directly.

      But in case of fancy combinations, then DSPs can be involved for other actions such as xcode.



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