Why a lamp tester or fuse tester? Testin cables, wires, lamps… belongs to a repair job and sometimes this becomes too cumbersome since one has only two hands and too often, one has to hold the part being tester and the two probes of an ordinary continuity tester all at the same time.

This fuse and lamp tester enables easy testing of lamps and fuses by using the conductivity of the human body. One of the test probes is connected to the part under test while the other probe is hel dby the normal hand.

The digital sinewave generator has the advantage that only few components are needed to generate signals with high amplitude constants and variable within a ver wide range of frequencies. The circuit shown here generates a sinewave signal. Other signal forms can also be generated by changing the values of R1…R8.

This infrared detector circuit uses a passive IR-detector component PID20. It converts heat radiation into electrical impulses. The output voltage of the PID20 increases when an object comes close to it, this object must be warmer than the surroundings.

You may use this speaker balance calibrating circuit when using a stereo amplifier, there are many possible mechanical problems that may influence the amplifier’s output performance. The usual culprit is the mechanical potentiometers which are not rarely unsync in their stereo resistance pads. This results to unbalanced volume levels on the audio channels. Most good stereo units have a balance control to compensate for this imbalance.