The technology described herein can be embodied in a method that includes receiving a first signal representing an output of a speaker device, and a second signal comprising the output of the speaker device, and an audio signal corresponding to an utterance of a speaker. In one configuration, a voltage clamping device such as a metal oxide varistor is utilized in a ground fault circuit interrupter product for handling transient surges and overvoltage conditions and is placed in series with a solenoid coil. Each specific marker layer combination may employ two or more layers. Current is only supplied to the trigger output if both trigger control paths sense a crash-level shock and are armed. The software monitors the at least one detector for an incoming IFF signal and the software initiating the flow of electric current through a selected set of the plurality of emitters responsive to receiving the incoming IFF signal from the at least one detector. The display unit has a main housing which contains a light source that may include a diffuser and a cover lens or glass that includes one or more layers of the artwork to be displayed.