The Honeywell 420-I is a digital-to-analog converter, also known as an analog output converter, designed for use within Honeywell gas detection systems. It connects to Vulcain transmitters via an RS-485 daisy-chain network (Modbus), translating digital signals into standard 4-20 mA analog outputs. This allows centralized monitoring and integration with Building Management Systems (BMS). The module supports up to eight dedicated 4-20 mA outputs, and can process readings - such as average, minimum, or maximum - from up to 16 transmitters