I recently had to replace a Callmaster II customer service phone with an exact duplicate. But on the replacement, the customer gets a tone every 14 seconds through her headset, which can also be heard by the other party. The original console did not have this annoying tone, but I can't figure out what may be causing it on the replacement. Any help would be greatly appreciated. It happens any time the phone is off the hook, but doesn't seem to be tied to how long the phone has been off-hook.