Abstract: A test device for testing automatic door systems has a test circuit including a display, a micro-controller, a memory for storing data and a test program, and a control switch for controlling operation of the test program by the micro-controller. The test device is installed by interposing the test circuit between the controller and sensors of the automatic door system. A selector switch on the test device is moveable between first and second positions. When the selector switch is in the first position, it completes a data path between the test circuit and the controller and blocks the exchange of data between the sensors and the test circuit and the first connector. When the selector switch is in the second position, it completes a data path between the test circuit and the second connector and blocks the exchange of data between the controller and the test circuit and the second connector.