In addition to the four NACs found on the 4009 System Board, an aftermarket NAC option card is available to provide four additional Class B (Style Y) hardwired NACs. To support Class A (Style Z), you must install a Class A adapter option card that mounts onto the NAC option card (Refer to the 4009-9808 Class A Adapter Option Card Installation Instructions [574-326]). Each 4009-9807 NAC option card supports up to two Class A option card(s).In addition to the four NACs found on the 4009 System Board, an aftermarket NAC option card is available to provide four additional Class B (Style Y) hardwired NACs. To support Class A (Style Z), you must install a Class A adapter option card that mounts onto the NAC option card (Refer to the 4009-9808 Class A Adapter Option Card Installation Instructions [574-326]). Each 4009-9807 NAC option card supports up to two Class A option card(s).