Maxitrol Selectra A1494 Amplifier supplies output voltage to the M valve. The Selectra Series 94 systems are designed for use with atmospheric and direct-fired burners like in furnaces, ovens, etc.. Series 94 is used in either 'remote' or 'self-contained' systems, along with components common to either configuration. A remote system contains an amplifier with a separate temperature selector. A room override thermostat is optional with a remote single-dial selector. The self-contained system has the amplifier/selector combined as a single unit. Common items include temperature sensors, mixing tubes, and modulator-modulator/regulator valves. A dual remote temperature selector is also available and is primarily used for paint booth ''spray/dry'' applications.