AST Model SRX-CT-4 O2 sensor is designed for respiratory gas analysis and is a drop-in replacement to Teledyne T-7, City Technology MOX-4, AII PSR-11-77 and PSR-11-77CT-4 O2 sensors. This sensor shows excellent linearity and accuracy even under varying ambient conditions. AST Model SRX-CT-4 O2 Sensor, among other analyzers, is used in Teledyne TED 191T, TED 200T, TED 200T7, TED 60J, and TED 60T analyzers. Its innovative design with proprietary Pb anode structure provides with excellent stability and ensures full utilization of the anode without signal drift thus minimizing frequent calibration requirement. Sensor is designed, developed and manufactured in the USA.