Smart sensors plug into Series D12, allowing it to detect any of 32 toxic and combustible gases. Two-wire transmitter communicates via Hart (standard), Modbus (optional), or 1 trouble and 2 alarm relays (optional). Unit logs data and displays concentration history graphically. Self-testing sensors ensure reliable performance. Transmitter operates in Class 1, Div 1, Group B, C, and D areas, and is intrinsically safe when loop-powered.