A receiver receives a signal and samples it at multiple sample points. When rotating, the buffer brush acts as a centrifugal pump. The frequency synthesis circuit includes a sequence of adder-and-register units that select one of the VCO clock phases. An electronic document requiring a notarized signature by the signatory is retrieved from the server. A communication unit arranged in the main body can communicate with the electronic-information storage unit to write information in or read information from the ID chip. Systems and methods for adjusting the viewing characteristics of the display system are also disclosed.