Most of the 7900 series Cisco IP phones can be configured for dual-line capability. The most notable exceptions are the 7936/7 series conference phones and the 7921 series wireless phones that are both considered single-line. In this case, dual-line function allows an incoming call to display on an IP phone when that phone is off-hook or otherwise already in use. This is not to be confused with a telco-enabled call-waiting feature that may be installed on an analog, CO line. For information on how to use that feature, reference this, earlier post.
There may be reasons why you wouldn’t want a phone to display more than one active/alerting call at a time. If, for example, you have a call center or other type of hunt group function, you may not want additional calls to be coming in to a hunt group member when that person/phone is already engaged.
Assuming that you do want additional calls to display, however, you need to configure the DN to display the second incoming call. To do this, you must create the DN with a dual-line entry. If you create a DN without dual-line capacity, you cannot go back and add this configuration option later. To add it later, you have to delete the DN and recreate it as dual-line. After you have enabled it for dual-line, you can then decide whether or not you want incoming calls to roll to the phone’s second channel or not. This is done through ‘huntstop’ commands. Here is a DN configuration that includes the line ‘no huntstop’:
ephone-dn 10 dual-line number 112 label Mary Smith 112 description Mary Smith 112 call-forward busy 100 call-forward noan 100 timeout 10 no huntstop
No huntstop, in this case, (almost literally) means ‘don’t stop hunting for the next available channel or DN’. Without this, an additional call coming into an off-hook phone would audibly alert the user to the new call, but then would roll to one of the ‘call-forward’ destinations. With the ‘no huntstop’ command configured though, the user may choose to take the call based on its caller-id.
It is possible to configure this DN with both ‘no huntstop’ and ‘huntstop channel’. You would want to do this if you wanted to control call flow and to allow it to move from DN to DN or phone to phone. Here is how Cisco describes these two functions: “The no huntstop command allows calls to continue to hunt to other ephone-dns if this one is busy or does not answer. The huntstop channel command disables call hunting to the second channel of this ephone-dn if the first channel is busy or does not answer. ”
Outside of this simple functionality, there are some pretty nifty things you can do with these huntstop commands including configuring multiple DNs with the same number and using overlays to manipulate the number of calls that any one phone can handle at any one time. This is particularly useful for a receptionist’s phone.
