The Regulus RC21PRO analog room thermostat measures temperatures from −50 to 300 °C, depending on the connected sensor. It supports NTC and PTC sensors and has an SPDT relay output for system control. It can be powered by 230 V AC, 115 V AC, 12 V AC/DC or 9–24 V AC/DC.

• Type: Analog
• Temperature resolution: 0.1 °C
• Inputs: 1 analog NTC/PTC sensor input and 1 digital external contact input
• Sensor types: NTC 10 kΩ at 25 °C, β=3435 (−40 to 125 °C); NTC 5 kΩ at 25 °C, β=3980 (−40 to 80 °C); PTC 990 Ω at 25 °C, KTY81(2)-121 (−50 to 150 °C); PTC 1 kΩ at 100 °C, KTY84-130 (−40 to 300 °C)
• Outputs: 1 SPDT relay, 250 V AC, up to 8 A for resistive loads; optional SPST relay output, 250 V AC, up to 5 A for resistive loads
• Maximum common terminal current: 12 A
• Power supply: 230 V AC ±10% at 50/60 Hz, 115 V AC ±10% at 50/60 Hz, 12 V AC/DC ±10% or 9–24 V AC/DC
• Serial port: TTL, Modbus RTU protocol, 9600 baud, 8-bit characters, even parity, 1 stop bit
• Measurement range: −50 to 300 °C
• Resolution: 0.1 °C or 0.1 °F between −19.9 and 99.9
• Accuracy: ±0.5 °C and 1 digit at 25 °C, plus the accuracy of the connected sensor
• Display: 3-digit red LED, 14 mm high
• Display dimensions: 34.5 × 76.5 mm
• Mounting cutout: 29 × 71 mm
• Terminal connection: For cables up to 2.5 mm² in diameter
• Housing material: PC+ABS plastic at the rear and PC on the front panel
• Front panel protection: IP65 with sealing gasket
• Operating temperature: −10 to 60 °C
• Storage temperature: −25 to 70 °C
• Storage humidity: 30–90% RH, non-condensing
• Maximum switch temperature: 60 °C
• Pollution degree: 2
• Rated impulse voltage: 2.5 kV
• PTI of insulating material: 175 (250 for the circuit board)
• Electric shock protection class: II
• Relay switching type: 1.B, micro-disconnection
• Software class: A