we are facing following issue:
Our CC agents are using 7841 phones for extension mobility. However, when the headset's AUX cable is connected, they won't be able to log in. The phone remains in the registering state or seems to be completely out of order/cut off from power. The solution is sometime pulling the AUX jack and trying to log in. Provisioning the phones with additional power supplies seems to help partially but not always and it's not a solution anyway.
If the phones remain in registering state then you can take a packet capture from the 7841 to see where exactly the registration fails. However if it seems to cut off from power then it is most likely a compatibility issue with the headset, have you confirmed with Plantronics about the compatibility of this headset with the 7841 Ip phones?
What is the firmware version? and CUCM Version ?
Does it work without extension mobility ??
May be you are hitting bug
What do you mean by below comment ? does phone is powered off when headset is plugged in ??
"seems to be completely out of order/cut off from power.
The phones are running sip78xx.10-3-1-12, and UCM has 10.5.2.10000-5.
Without extension mobility, the phones seem to work fine with the headsets. Only CC agents are affected that use shared working places when they try to log in. Even with EM, once they are logged in, they can make calls without problems.
They do the following woo-doo to be able to log in:
They try to log in, when it doesn't work (it probably won't), they pull the network cable (PoE) and the AUX cable. Then, they plug in the network cable, the phone comes up, they log in and plug in the AUX cable. After that, they are able to make calls.
In the beginning of the above procedure, if they don't pull the AUX cable of the headset, the phone may not start at all, it remains lights off.
We thought the AUX port pulls power and that's why we added power supplies to the phones. With a power supply, the phone won't remain lights off but the pull out plug in woo-doo remains the same.
If the headsets are compatible with this model of IP phone then this will require investigation through packet captures from the IP phone and detailed callmanager service traces while recreating the issue.
Just to make sure it is compatibility issue with headset, try to test single phone with another different model of cisco compatible headset