Nortel NT5B37GA-93 DID Trunk Cartridge (Refurbished)This Direct Inward Dialing Norstar Trunk cartridge routes calls from the public network directly to Norstar station sets, bypassing an attendant and therefore reducing traffic to the central answering position. This Norstar card provides access for up to 4 central office lines. This Norstar trunk cartridge is compatible with the Modular 8x24 (Release DR4 or higher) and the Modular ICS and supports disconnect supervision, but does not support CMS CLASS