Circuit Protection Devices Bourns manufactures and supplies a wide range of circuit protection technologies, including fuses, PTC thermistors, varistors, GDTs, resettable thermal cut-offs, surge protection devices, hybrid protectors, discrete semiconductor solutions, and more. Reliable surge protection is a critical design consideration to help ensure operational reliability of consumer electronics, industrial/communication equipment, automotive, battery charging, energy storage infrastructure, and renewable energy harvesting ecosystems.