... . Optional function: Bi-directional voice communication,Central management software provided(optional) Specification ItemDescriptionOperation systemLinuxVideoVideo input/output4 ... transmission (optional)3G WCDMA, CDMA2000, TD-SCDMA system optional; Compatible with GPRS, EDGE; Built-in ... , x4, x8, x16 GUIGraphical User InterfaceSetup system parameters through the remote controlAlarmInputUp to 6 channels ...