... playback simultaneously support 3G and wifi 3G DV 4 ch Bus security system with 3g ,GPS,wifi ,G-sensor Features audio ... case of power lost1.1.1. Typical ApplicationsApplications: bus, school bus/staff bus, logistic trucks, coach bus, taxies, train/metro/light rail, vesselsTopological graph ... View: Back View: 1.1. Front Panel Definitions 4 ch Bus security system with 3g ,GPS,wifi ,G-sensor