Q-See 8-Channel HD Analog DVR: 1TB HDD, H.264, Mobile Surveillance, 8 Channel Simultaneous Local Playback Backup Via PC, Flashdrive or USB Hard Drive Up to 128 Simultaneous users (bandwidth permitting) Mobile Compatibility: iPhone, iPad, and Android Instant Email Alerts and Mobile Notifications Supports 1 SATA HDD up to 4 TB