The Norstar Nortel ISDN-PRI Enabler Soft Key is the PRI keycode for Norstar MICS business telephone system. This key is required in order to configure the Digital Trunk Cartridge (DTI Card) as a PRI Card. Norstar MICS PRI. Norstar Primary Rate Interface. Provides Caller ID and DID capability for Nortel Norstar MICS NT7B74GA.