This ESI IVX second generation E2 612 port card is designed for the ESI IVX E-Class, X-Class, 100, 200, 600, and 1000 phone systems. The E2 612 supports up to six phone lines and twelve digital extensions. This card is compatible with ESI CS-50 and CS-50L phone systems. Compatibility with the CS-200, CS-600, and CS-1000 is available through an optional backplane adapter.