The Series 650 Temperature Transmitter by Dwyer® has a 4-20 mA signal. It also has a temperature that ranges from -55 to 180°C. This is a two-wire operation product. On the other hand, the Series 651 Temperature Transmitter is an RTD or a thermocouple input. It has a 4-20 mA signal as well. The Model 652-0 Programmable Transmitters is indicated for voltage or potentiometer output, and is indeed isolated. Series BTO Bimetal Thermometer comes with transmitter output and 2 metal stem with 4-20 mA output. Series TTE Explosion-Proof RTD has selectable ranges for users, and an optional LCD Display.