Fasten on the side of its walls pieces of rubber hose — doors of your car are always safe.
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If you want to cut the pipe lengthwise into halves, it is necessary to outline its diametrical plane. It's easy to do and without any measuring devices by using a sheet of paper....
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To debug transistor-based hardware is much easier if you have the regular store stable voltages. Two adjacent shoulders of the bridge rectifier V1, V2 connect the unit Zener diodes V3 —...