Panasonic KX-TDA5176 8-Port Proprietary Analog Extension CardCompatible with KX TDA50G and KX TDA50 Telephone Systems 8 Port Analog Proprietary Expansion Card may be used to connect This card is most commonly used when a customer currently has KX T7700 Series Phones that they were using on a Panasonic Analog Telephone System and wants to upgrade to a Panasonic Digital Telephone System and reuse their phones. 8 ports per card. Supports KX T7700 Series (APT), DSS and Voice Mail. 2 cards max per system.