Active Caller ID is full-featured caller ID detection software that will turn your PC into an advanced caller ID device. It uses your modem and caller ID service provided by your local phone company in order to identify who's calling. Active Caller ID has its own built-in address book that will keep your contacts in one place where they will always be easily available. It allows you to associate a ring audio file (MP3, WAV, MP4, OGG, M4A, AAC, AC3, FLAC, AU, and VOC) to per contact. It also allows you to associate a photo to per contact and supports two detection modes.