OTIS Instruments OI-6000 Fixed Gas Detector, Carbon Monoxide (0-1,000 PPM). Includes: Explosion Proof Design, 4-20 mA & RS-485 MODBUS Signal Outputs. Requires 12 to 35 VDC Input Power (3-Wire). OI-6000-EC-CO-X-X-O. Note: As options, OTIS OI-6000 series sensor assemblies can be equipped with a 900 MHz GEN II Radio and/or Two Dry Contact Relays.