Apparatus and armrest for adjusting height of resting plate

An apparatus for indicating a height of a resting plate supported by a first supporting means and a second supporting means comprising:

• a variable resistor comprising:
• a track connected to the first supporting means;
• and
• a slider connected to the second supporting means, and movably disposed on the track;
• and
• a display electrically connected to the variable resistor,
• wherein a position of the slider on the track is changed according to a movement of the first supporting means,
• the variable resistor is configured to detect a resistance depending on the changed position of the slider on the track, and measure the height of the resting plate based on the detection, and
• the display is configured to display the measured height of the resting plate.

An armrest comprising:

• a resting plate configured to rest an object thereon;
• and
• an apparatus for adjusting a height of the resting plate comprising:
• a hydraulic means configured to support the resting plate, and configured to move along an axis to adjust the height of the resting plate;
• and
• an activator connected to the hydraulic means, and configured to activate and control the hydraulic means to move along the axis to adjust the height of the resting plate, or deactivate the hydraulic means to stop at the adjusted height, based on first external force on the activator.