This part is a kind of semiconductor called KX-T7730.
Function of this product has Proprietary Telephones Quick Reference Guide.
Manufacturers : Panasonic
Image and pinout :
Some of the text within the PDF file :
Proprietary Telephones Quick Reference Guide KX-T7720/KX-T7730 KX-T7731/KX-T7735 Model KX-T7736/KX-T7750 Important Information When you ship the product: Carefully pack and send it prepaid, adequately insured and preferably in the original carton. Attach a postage-paid letter, detailing the symptom to the outside of the carton. DO NOT send the product to the Executive or Regional Sales offices. They are NOT equipped to make repairs. Product service: Panasonic Servicenters for this product are listed in the servicenter directory. Consult your authorized Panasonic dealer for detailed instructions. WARNING: TO PREVENT THE RISK OF FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE THIS PRODUCT TO RAIN OR ANY TYPE OF MOISTURE. THIS HANDSET EARPIECE IS MAGNETIZED AND MAY RETAIN SMALL FERROUS OBJECTS. IM [ ... ]