Abstract: An isolator with resistive termination and carbon steel housing wherein required magnetic performance is combined with improved efficiency of transmission of heat from termination to the heat sink. The improvement is achieved due to the copper/aluminum plug that mechanically and electrically connects the soldering base of termination to the base of isolator, which in operation is installed on the heat sink. The plug is pressed into the housing from the base side to provide tight coplanarity tolerance to exposed end of the plug and the base without any secondary machining. The termination is soldered to the opposite end of the plug, which is flush to or slightly above the top surface of the housing. Thus, magnetic flux required for operation of isolator is looped through a material having good magnetic susceptibility, and heat from the termination is transmitted to the heat sink through a material having high coefficient of heat transmission.