Panasonic KX-TDA0290 PRI Card PRI23Good ConditionISDN Primary Rate Interface Card (PRI23)23 Ports per card23 B channels + 1 D channelExternal channel service unit requiredRequires 1 free slotUse with KX-TDA100, KX-TDA200, KX-TDA600, KX-TDE100, KX-TDE200, and KX-TDE600 systems..