Modern vehicles are crammed with sophisticated electronics such as car phones, CD players, radios, alarms, digital dashboards, fuel tank senders, ECUs and vital airbag and seatbelt pre-tensioner circuity. All these devices can be damaged or degraded by transient voltage surges and spikes caused during the jump starting process. By using PROSAF and PROJUMP spike and surge protection devices you totally remove, the danger of damage to any on-board electronics. The PROJUMP units are designed for use when jump starting vehicles and provide total protection to both vehicles from the effects of spikes and surges. The PROSAF units are specifically designed for use in the workshop and are connected across the battery terminals to provide total protection from the effects of spikes and surges. The PROSAF units are ideal for use when carrying out routine car maintenance and will provide protection even when welding. Note that there are many products that make similar claims but beware! Many of the cheaper units use a single component that is both cheap and completely inadequate. The PROJUMP and PROSAF are the only ones that are guaranteed to clip the surges and spikes and provide total protection.