Abstract: An adapter converts a conventional two-way end of train unit (EOT) to a dual purpose EOT that can be used conventionally for those trains not equipped with a power line for the new electrically controlled pneumatic (ECP) freight train brake standard but which can be quickly and inexpensively modified to change the function of the EOT from the normal two-way EOT function to the ECP EOT function as defined by the Association of American Railroads (AAR). An electronics package or adapter plugs into the battery compartment of the standard EOT and makes connections with the standard EOT electrical connectors that are located in the battery compartment. This adapter is designed to communicate with the standard EOT microprocessor and to configure the standard EOT in a way that the standard EOT in combination with the adapter functions as an ECP EOT rather than as a standard EOT.