How can I do this? The phones are all display w/ 8 buttons. Thanks for the help.

More info is needed. Regardless, with any digital system, you are going to run into severe problems due to ring voltage. Trying to run 2 digital phones off of one digital extension is risky as the very best, disastrous at the worse. Draining voltage can crash the system just as easily as high voltage spikes.

You can't run two KT's off one digital port. You CAN assign an immediate call coverage button for one extension on the other extension.

If your software version is 7.2 or higher, you can put both extensions in an all-call hunt group and direct calls to the group.

You could put a call coverage key for a phantom ext. on both phones, but yes I think we need some more info as to what you are trying to accomplish.