The MSD has three heated zones:
Ion source (Source or MS Source in the software)
Mass filter (Quad or MS Quad in the software)
GC/MSD interface (Thermal Aux 2 in the software)
Each of these heated zones has a heater cartridge and temperature sensor. The ion source and mass filter heaters are powered and controlled by the MSD. The GC/MSD interface is powered and controlled by the GC.