A kaleidoscope has a main body, a tubular cover and an object cell. Spacers are provided for insertion into the grooves and have radial outward projections for engaging between shield segments and enclosure rings. Once the received signal power level has been measured, the power level data based on the received signal power level is automatically transmitted from the receiving station back to the source of the measured signal over the backhaul link. A determination is made as to whether a second byte caching system is available. The processing unit receives the control signal and operates the video unit according to the control signal or operates the multimedia device through the communication port. The ability of the electron source to move makes it possible to extend and retract it simply by switching the operating current on and off.