D.I.D is one of good feature of ISDN PRI. It is just opposite to D.O.D. feature.
D.I.D.:- It means direct inward dialing. In normal company's telephone structure, call are routed through receptionist. Receptionist transfer the calls to concern person. but this process irritates callers. They need to be on hold for a long time. They get frustrated and many times, company may loose good order. Customer wants to speak directly to the person he wishes to talk. So D.I.D. feature enables callers call directly to the concern person. Officers have their direct incoming numbers. Their extensions work as intercom as well direct incoming number. So it gives a comfort to caller as he gets direct in touch with concern person. Customer gets satisfied.