For use with 5201-2 or 5203-2 Operators. The Taco Heat-Guard thermostatic valve consists of an angle globe type valve body and an operator. It is a self contained, wireless, automatic, modulating control valve for use in hot water or two pipe steam space heating systems. It senses changes in temperature and automatically increases the flow of heat in response to a temperature drop, or automatically decrease it in response to a temperature rise.It may be used to control baseboard, convectors, and radiators