Abstract: A system for thermal angioplasty provides electrical power to a heating coil located inside a dilatation balloon, receives a signal from a sensor at the coil indicating its temperature and also receives signals from balloon sensors indicating the temperature at their respective positions. An isolation transformer is used to provide RF power and the sensor signals are optically coupled to provide increased electrical isolation for the patient. The heating coil temperature sensor signal is compared to high and low temperature limits and if either is exceeded, a fault signal is generated. The sensor signals from the balloon are compared to predetermined high temperature limits and if exceeded, fault signals are generated. The current drawn from the battery is compared to a predetermined current level and if exceeded, a fault signal is also generated. Upon generation of any of the fault signals, the electrical power to the heating coil is interrupted by fault detection circuitry.