The RKI low cost CO/H2S transmitter is a highly reliable and very cost effective basic 4-20 mA transmitter for the detection of carbon monoxide and hydrogen sulfide. The electronics are protected inside a plastic enclosure to avoid damage from mechanical abuse, water, dust or corrosion. Sensors for H2S and CO are long life and typically last 2 - 3 years. The transmitter operates from 24 VDC (11VDC to 30 VDC), and provides a 4-20 mA signal which can be connected to a wide variety of controllers. The low cost CO/H2S can be used either indoors or in semi-enclosed areas. The only tools required to calibrate the low cost CO/H2S transmitter are a voltmeter, screwdriver, and calibration gas. The zero and calibration functions are performed by adjusting potentiometers on the amplifier board. The amplifier board has test jacks for the connection of a voltmeter for calibration purposes, and the sensor response is viewed on the voltmeter as a 100mV to 500mV signal. Field calibration can be performed easily and quickly by one person.