A pressure-activated membrane switch and methods of use are provided. The pressure-activated membrane switch includes an electrically-conductive membrane, and a compliant conductive material having an electrically-conductive inner surface, wherein contact between the electrically-conductive membrane and the electrically-conductive inner surface of the compliant material is configured to cause an electrical circuit, of which the switch is a part, to close. The pressure-activated membrane switch further includes a plurality of spacers dispersed between the electrically-conductive membrane and the compliant conductive material. The plurality of spacers form one or more gaps between the electrically-conductive membrane and the compliant conductive material, and, with an application of pressure against the compliant conductive material, the compliant conductive material is configured to deform between the one or more gaps to contact the electrically-conductive membrane.

An overcurrent protection device according to an embodiment of the present disclosure may include a first electrode disposed substantially parallel to a second electrode. A material may be disposed between the first electrode and the second electrode. A plurality of conductive material nodules may be disposed in the material between the first electrode and the second electrode, including a first conductive material nodule at least partially contacting an inner surface of the first electrode and a second conductive material nodule at least partially contacting an inner surface of the second electrode and the first conductive material nodule. In response to an overcurrent condition the material may be configured to expand, such that the contact between the first electrode, the first conductive material nodule, the second conductive material nodule, and the second electrode is at least partially interrupted.

An item may have regions that are illuminated by light from a light source. The light source may be based on components such as light-emitting diodes. Diffusing material, luminescent material, and other light-adjusting materials may be incorporate into the item. The item may include movable structures such as movable keyboard key members. Light-emitting diodes may be mounted on a substrate. The substrate may be coupled to keyboard key members, additional substrates, or other structures in an item. The item may include a layer of fabric and layers of other material. Openings in the layers of material may be configured to receive light-emitting diodes. Opaque layers of material may have patterned openings that help define shapes for the illuminated regions.

A method of operating a contact sensor and a method of calibration of a contact sensor. The contact sensor comprises an array of discrete and spaced apart sensing elements (102, 202) connected to a resistive element (101, 201) with the location or size of a contact being detectable by measurement of one or more electrical parameter(s) relating to impedance steps along the resistive element (101, 201) is described. The method of operating involves determining a length of the sensing element between the contact and the resistive element and using this to compensate for a parasitic resistance present in the measured resistance of the resistive element. The method of calibration comprises applying one or more calibration contact(s) at a plurality of locations across the sensing elements (102, 202) to be calibrated; monitoring changes in at least one electrical parameter during the time that the calibration contact(s) are applied; and recording information relating to variation in the at least one electrical parameter, the information allowing assessment of the variation in each impedance step across the measured sensing elements. This enables the later use of the sensor to take into account any variation in the impedance steps.