7-Way Blade Tester and Trailer Emulator w/LED Display Plug these testers into any car connector and you will have an instant test of running light circuits. Features LED display to show completed circuit for the running lights, left turn signal and right turn signal. Auxiliary circuit LED display is included on the 5-way tester, auxiliary and electric brake are included on the 6-way tester and auxiliary, electric brake and battery charge are included with the 7-way tester. One piece units with internal ground. Dust cap included with 5-way tester and 4-way tester can be attached to key chain to always be readily available. Proper installation and set-up of a brake control when a trailer is not readily available is possible with the 7-way tester. Current Monitor testing device is designed to assist in determining whether a tow vehicle's 7-way blade car end connector has been wired properly. (Current Monitor is an excellent diagnostic tool for installation, setup and troubleshooting of electric trailer brake controls.)