The Maxitrol TS394-3B-48FQ Temperature Sensor is a part of the Selectra Series 94 System.  The sensor has a 3" x .19" diameter probe.

Selectra® systems from Maxitrol maintain precise, stable gas-fired temperatures. Selectra's unique electronic ModulatorRegulator valves control gas flow with instantaneous response and continual adjustment. They are the superior alternative to mod motors and butterfly valves. OEM or retrofit applications include environmental climate control, as well as industrial or commercial heating processes. All fuel gases are compatible - capacities to 30,000,000 Btu/h. Available standard companion electronics include temperature selectors, amplifiers, and temperature sensors, in a variety of configurations. The amplifier supplies output voltage to the M valve.

Selectra® Series 94 systems are designed for use with atmospheric and direct fired burners (used 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 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. A "K" thermocouple (not supplied by Maxitrol) may be used with "K" suffixed amplifier/selectors.