Trying to find documentation on how the Busy lamp fields (Pn NT8B91) are supposed to behave on a Norstar 7310, but can't locate any manuals; nortel.com-. It seems that the bottom half of the block lights up when the buttons top intcm is in use and vice versa. Pressing the shift key and monitoring made no dif. Hard to believe this is how it's supposed to work. Thanks for any leads.