The ISOA are four-terminal resistors that are offered in two electrical configurations: first the single resistor option where the resistor is connected between terminals 1 and 3, denoted by the part number code R1; the second option, denoted by part number code N1, integrates an NTC thermistor in the same package with the resistor, where the resistor is connected between terminals 1 and 4 and the NTC thermistor is connected between terminals 2 and 3. The phase change thermal interface material may be added to either configuration and this is denoted by part number code T1 for the resistor-only option, or NT for the resistor with the NTC thermistor option.