In addition to the versatility of this tester, we also designed in some features to make servicing trailer and vehicles simpler. For example, the tester checks for cross shorts between circuits. This may not seem like a big deal, however, if it occurs between the turn signal and trail light it could go undetected. In addition to the error checking circuits, we also included a brake test circuit which tests the electric brakes and brake controller; an amp meter for monitoring current draw; we include all standard trailer mating connectors; and finally, a power source select switch and power supply for operating the tester on 120VAC or 12 VDC.