4-20mA analog output for direct communication to DCS system or RS485 ModBus RTU output optiona. Relay output for connecting external device LCD display screen(LED display screen optional) Advantage: Sensor module(block) design on -spot replacement s and automatically distinguish sensor fault and current display fault simultaneously. When the sensor out of service or the sensor fails, the user can check and solve the problem by replacing spare modules,saving the time and cost. The LCD display and LED display module can be interchanged, supporting swift hot swap,support plug and play functionality. The sensor module and the connection interface in the detector have jack and plug prevent improper insertion.Just spin and press the plug gently,the plug can be inserted the jack. The sensor module of the detector can be replaced by the same type module and the different gas sensor module,and different range sensor module. The detector can distinguish and operation itself. Whatever the sensor module is chosen to replace the original one, there is no need to re-calibrate it. The detector automatically distinguishes the sensor module, reads the ex-factory calibration value and the related setting value and operates detecting when the self-inspection is done. Password verification for repeat operation, avoid fault operations. -40~+70 following compensation for accurate detecting. Twp grade visual alarms on-site and Relay (connected with audible/visual alarms or drive exhaust device). User-selectable alarm setpoint(s).