An appendant to existing vehicle door panel armrests that renders the arm support location more adjustable and the arm more comfortable. The arm member comprises a base, a slider receiver and a pivot portion. current sources with the negative output terminal of each source connected to a separate structure and the positive output terminal of the sources connected to a common anode located near the structures. The first control stage is biased under a high voltage and outputs one of the first control signal and the high voltage. As a result, a pen input display device of an ultrasonic pen input system is provided that prevents errors over the entire input area of the display panel without increasing power consumption or impairing operability of pen entry.