Abstract: An electronic breathing mixture control system which senses and controls oxygen component partial pressure of an underwater breathing mixture. Three oxygen sensors disposed within a mix chamber generate voltages proportional to the oxygen partial pressure in the mixture. These voltages are processed and compared with reference voltages using digital logic circuitry. The resulting processed signals control two light emitting diodes warning the user of improper oxygen partial pressure and in addition control a switch that actuates an oxygen valve which either restricts oxygen flow to the mix chamber or allows more oxygen to flow therein.