The Bartol Mag-Probe Solenoid Valve and Relay Tester is a Non-Contact Device that Eliminates Having to make a Direct Connection. You Do Not Have To Turn the Off Power and Most Tests Can Be Accomplished While the Equipment is Fully Operational. It is Not Necessary to Trace Wires or Use Schematics. You Do Not Have to Make a Direct Connection so it makes it Easy to Reduce Troubleshooting Time, which in turn Saves Dollars by Dramatically Increasing Productivity. No More Need to Follow Schematics to Isolate the Terminal Strip. You can Actually Go Directly to the Solenoid Valve and Conduct Your Test Without Making Contact.