PLEASE, PLEASE try and help me...I can't tell you how much this would be appreciated. I have a Panasonic KTS4100 4 line phone (2 corded phones in our office, and one cordless). I have NO IDEA how to use the INTERCOM between phones. It sounds like a small problem, and I can't believe I can't figure this out, but I just can't. There is an INTERCOM button on the right hand side of the number dial pad. I never had any reason to set up my phones with each one having an extension number or anything. When I pick up the phone, then hit the intercom button, there is just a high pitched tone in my earpiece, not heard anywhere else (for instance, it would be great if the other corded phone, in the back office could hear that tone when I am pressing the intercom button!, that's the whole problem!), the display on the phone lights up when I pick up the reciever, then when I hit the intercom button, the display reads: Intercom To - then a flashing black square. PLEASE PLEASE TELL ME HOW TO USE THIS INTERCOM. THANK YOU!!!!!!!!!!!!!!! My email is [email protected], phone numbers: cell: 610-731-1124, office: 610-640-9355, home: 484-320-8197, call or email anytime..hopefully very soon. Thank you, again.