In telecommunication, a low-power communication device is a restricted radiation device, exclusive of those employing conducted or guided radio frequency techniques, used for the transmission of signs, signals (including control signals), writing, images and sounds or intelligence of any nature by radiation of electromagnetic energy. Examples: Wireless microphone, phonograph oscillator, radio-controlled garage door opener, and radio-controlled models.
... is zero, then there is a repeated solution x, and this solution is real. (Geometrically, this means that the parabola described by the quadratic equation touches the ...