The ICD-PX440 4GB PX Series MP3 Digital Voice IC Recorder from Sony is a digital voice recorder designed for use in business applications. It features 4GB of internal memory, and supports up to 32GB of additional storage via its microSD card slot. The recorder features Sony's Intelligent Noise Cut function to reduce background noise while recording, and a track mark-based cue system allows for navigating individual recordings. 2 AAA alkaline batteries.