I have a small Norstar 3x8 KSU with standard punch down block. I connected an M7310 phone to the first pair on the block (blue-white, white-blue) and all the 7310 would do is display an arrow on one key which slowly fades, nothing else. I connected an analog phone to the first pair and got a tone that sounded like a pbx dial-tone. The KSU appears to be on the old side (maybe around 1990).
Is there a problem with the KSU? Or maybe its the phone. It would do the same thing when I tried an M2112.
Any help is appreciated
Thanks.

-Drew