... record, timing record, alarm record.8. Multi-plex: Support preview, playback, backup, network transmission simultaneously.9. Support multi-channel playback ... SCharacteristicsHW-SVR73044 chs video input, 1 chs audio input, D1 preview resolution, SATA HDD supported, USB flash drive, DVD-RW ... -SVR731616 chs video input, 4 chs audio input, D1 preview resolution, SATA HDD supported, USB flash drive, DVD-RW ...