A self-positioning device for a keyboard includes two protrusions adapted to be respectively formed on opposite sides of a corresponding leg, two stops each formed on a corresponding one of the protrusions, and two sectorial bosses adapted to be formed on a corresponding one of the recessed seats to correspond to the two protrusions. Each sectorial boss has a first edge and a second edge to selectively abut a corresponding one of the two stops. The selective abutting of the stops to the first and second edges enables support of the keyboard on a plan surface horizontally and inclinedly.

A personal digital assistant protection system for protecting a PDA along with receiving various PDA accessories. The personal digital assistant protection system includes a housing with an upper opening within an upper surface, and a tray removably positionable within the housing. The tray includes a support member that supports a PDA in a manner aligned with the upper opening when the tray is positioned within the housing. An auxiliary power source and other items may positioned within the tray.

A keyboard attached to a personal digital assistant (PDA) set having: a hinge unit including a connector to transfer a keyboard input signal to the PDA, and upper and lower hinge covers; a connection unit placed inside of the hinge unit, and can be attached in the front direction or the back direction to the PDA; and a keyboard body connected with the hinge unit, folded and unfolded about the hinge unit, having a typing board on an upper side and a front panel controller (FPC) keypad to input a key pressed on the typing board. Therefore, the keyboard of the PDA can not only be attached in the front direction or the back direction to the PDA, but also separated from the PDA, thus making the usage and maintenance of the keyboard convenient.

A technique for implementing a center key in a capacitive sense radial slider interface without use of center mechanical button. A user interaction with an array of capacitive sensors within the radial slider interface is sensed. It is determined whether at least a threshold number greater than one of the capacitive sensors within the array are concurrently actuated by the user interaction. A center key actuation is registered if at least the threshold number of the capacitive sensors are concurrently actuated.

A capacitance measurement circuit includes a current source, a switch, and a comparator. The current source is coupled to drive a current through a circuit node. The switch is coupled to the circuit node to switch the current into a device under test ("DUT") capacitor. The comparator includes first and second input ports. The comparator is coupled to compare a first voltage received on the first input port against a reference voltage received on the second input port. The first voltage is related to the current driven through the circuit node, a frequency at which the switch is switched, and a capacitance of the DUT capacitor.