Abstract: A portable or personal water filtration apparatus comprising upstream and downstream removable reservoirs and a back-washable filter interposed therebetween. The back-washable filter comprises an upstream housing and a downstream housing, inside of which are fitted a membrane cartridge and a slidable plunger. The downstream housing is rotatable relative to the upstream housing between two or more positions, including, for example, an open flow position, a closed flow position, and a back-wash position. In the back-wash position, the downstream housing and plunger are axially extendable relative to the upstream housing and membrane cartridge in order to obtain a charge of clean water in the plunger that may then be forced backward through the filter by returning the plunger to its starting position. This dislodges accumulated debris from the membrane and reverses the slowing of flow observed through repeated use of the filter.

Abstract: A guitar tuner includes a manually graspable body with a head projecting outwardly from one end driven by a motor inside the body to rotate about an axis. The head includes a slot shaped opening for grasping the key of a conventional instrument such as a guitar. An input sensor in the body detects a tone from the string of the instrument and converts it to square wave of the detected frequency. This is compared by a microprocessor with the closest adjacent intended frequency of the instrument selected which acts to drive the motor to tighten or loosen the string as required to attain the required frequency. A digital display provides a readout of the number and letter of the string concerned. The user can select any one of a number of different states of the device for use with different instruments or different tunings. The user can also override the automatic string selection in cases where the string is a long way from its required frequency.