This document presents two options you can use to resolve a situation
when, on Cisco CallManager 3.x, there is a second incoming call on a line and
you are unable to transfer any active call on that line. In this scenario the
Transfer button is grayed out. This problem occurs due to the limitation on the
number of calls per Directory Number (DN). When a new call arrives, both lines
are occupied and there is no free line to effect the transfer. This document
describes the workaround you can use in order to overcome this problem.
Note: The workarounds this document describes are not required for Cisco
CallManager 4.0 because the maximum number of Calls per DN is now database
configurable. Refer to
How Multiple Calls Per Line Work in Cisco CallManager 4.0 for more
information on this.
There are no specific requirements for this document.
The information in this document is tested using Cisco CallManager
version 3.3. However, this is applicable to these software and hardware
The information in this document was created from the devices in a
specific lab environment. All of the devices used in this document started with
a cleared (default) configuration. If your network is live, make sure that you
understand the potential impact of any command.
For more information on document conventions, refer to the
Technical Tips Conventions.
With the current implementation, an IP phone can only handle two calls
per line. When you transfer a call, the phone first initiates a new call
towards the transfer-to party and then transfers the first call. This means
that with every transfer there are two active calls on the line.
When Call Waiting is enabled, an IP phone is able to accept two
incoming calls on one line. Because of the requirement mentioned in this
document, you are not able to transfer any of those calls. This requires
another line instance in order to initiate the additional call towards the
When there is more than one line on an IP phone, the solution is to
disable Call Waiting and configure the first line with Call Forward Busy to the
If there is only one line on the IP phone, you can also disable Call
Waiting. However, in this case it is only possible to receive one incoming
call. A second incoming call is transferred to the Call Forward Busy extension
configured for that line.
Call Waiting can be disabled system wide or on a per line basis. These
sections illustrate how to perform both options.
Note: If you disable Call Waiting system wide, all IP phones are affected,
unless otherwise configured on specific lines.
Complete these steps in order to disable Call Waiting system
Select Service > Service
Parameters for the service Cisco CallManager.
From the Call Waiting Enable Flag drop-down menu select
At the top of the Service Parameters Configuration page, click
If you run a cluster environment, repeat steps 1 through 3 for each
Complete these steps in order to disable Call Waiting for a specific
Go to the Directory Number Configuration of the IP phone. From the
Call Waiting drop-down menu select Off.
Number Configuration Settings for more details.
Click Update and then click OK on
the message that appears.
For the changes to take effect, click Reset
Click OK in order to reset the