In one embodiment, a multimedia resource is shared among a plurality of devices based upon a physical location of an active wireless endpoint unit within a structure. The network proxy can intercept communications between the application layer protocol and the transport layer protocol. The system can combine reference images with display images in a consistent, scaled relationship and can display those images with a variety of lighting effects. Amplitude peaks of the periodic signal may be detected in the envelope detector, which may determine an average amplitude value based on the detected peaks.