An upgradeable test set is that includes a stimulator circuit to transmit test signals to an electrical equipment under test, a coupling to removeably couple at least the stimulator circuit to one of a plurality of front-end interfaces. The plurality of front-end interfaces include a first front-end interface having a first display and a first input device and a second front-end interface having a second display and a second input device. The first display and the second display have different display characteristics, and the first input device and the second input device have different characteristics. The one of the front-end interfaces communicates a test control parameter to the stimulator circuit and a response of the electrical equipment under test is communicated to the one of the front-end interfaces. The case is configured to enclose the stimulator circuit, the one of the front-end interfaces, and the coupling.