A tied tea ball equipped with a serving string by which the tea ball can be lowered into and removed from a vessel of water. In some examples, the DCC circuit may generate a pulse in response to a falling edge of an input clock signal, delay the pulse based on a control voltage, adjust the falling edge of the input clock signal based on the delayed pulse to produce an output clock signal, and adjust the control voltage based on the difference between a duty cycle of the output clock signal and a desired duty cycle. The one or more hardware processors generate first and second presentation displays of the mock trial, each having an arrangement of content that may include a live-action video, a pre-recorded video, an image, interactive actuators or icons, text, or combinations thereof. The sensor unit comprises a capture surface area and a piezoresistive detection system, for direct detection of stress change of the sensor unit when applying an electrical field over the piezoresistive element. The panel driving apparatus and the panel driving system generate a variety of control signals, which are programmed by the microcontroller depending on the specifications for a particular panel, and thus they are applicable to various types of the panels having different specifications, without need to be manufactured as ASICs, thereby reducing the manufacturing cost.