The GE 28112EE3-a was made by Thomson with the GE name. The manuals for most of these phones are available here: http://www.home-electronics.net/user_guides.asp . The direct link to the manual is http://www.home-electronics.net/USER-GUIDES/28112_DOM_EN_CL_IB.pdf .
What type of beeping are you hearing? If you are hearing a beep every seven seconds from a handset, the solution is to recharge the battery. If the battery won't hold a charge, then replace the battery with a 5-2721 Nickel-metal Hydride battery.
The handsets can also beep for about 2 minutes if another handset or the base pages them. This is a locator tone. Just press the Talk/Call Back button or the Tone/Exit button on each handset.
I hope this helps.