A perpetual day reminder calendar consisting of display stand, date indicating cubes, day indicating plates and month indicating plates uniquely styled for ease of operation and clarity of information. A parameter conversion unit is configured to receive position information, which is representative of spatial positions of sound sources of the audio input signals, and spectral power information which is representative of a spectral power of the audio input signals. The method includes transmitting a frequency-hopping pilot beacon among the plurality of second frequencies. Each signal amplifier has a predetermined gain so that zeros of the transfer function are outside the desired frequency band. The information displayed on the visual display system may be substantially or entirely immune to stray electric fields. The charging circuit is disposed in the base and the charging circuit has a first electrical connector.