Littelfuse PolySwitch and POLY-FUSE products are Polymeric Positive Temperature Coefficient (PPTC) devices which provide a resettable overcurrent protection alternative, by reducing warranty, service and repair costs. Suitable for situations where frequent overcurrent conditions happen or constant uptime is needed, resettable PPTCs are generally employed in consumer electronics, power line, I/O port, telecom, process control and medical equipment protection applications.
PTCs increase resistance as temperature rises due to enhanced flow. Created to restrict unsafe currents while providing constant safe current levels, resistance will 'reset' automatically when the fault is removed, and temperature returns to a safe level.
The company's TSM250 PolySwitch Resettable PPTCs feature two 250V Telecom PPTCs in a single plastic housing to give tip and ring overcurrent protection and support compliance with ITU-T K.20, K.21, and K.45 as well as Telcordia GR-1089 intra-building. These surface-mount devices guard against damage produced by power cross, and power induction surges with fast time to trip. The PPTCs are excellent for secondary overcurrent protection in Customer Premise Equipment, Central Office, and Subscriber Line Interface Cards.