portable systems usually monitor their battery input to obtain an early warning of a loss of battery voltage
http://www.edn.com/archives/1997/091297/19di_08.htm
useful for any low level RF work
http://sound.westhost.com/project74.htm
It is a servo tester based on 556N chip. PCB design files are provided.
http://www.speedy-bl.com/servo-e.htm
http://www.web-ee.com/Schematics/Simple%20Superhet/simple_het.htm
in picofarad range
http://www.e-insite.net/ednmag/archives/1997/090197/18di_04.htm
http://www.uoguelph.ca/~antoon/circ/src.htm
suitable for measuring audio circuits
http://www.jensen-transformers.com/as/as048.pdf
Some examples of the phenomena of general relativity are simulated. This provides a graphical sight on the main general relativity concepts. The simulations include solutions in 3D (XY +time) and 4D (XYZ+time) spaces.
http://www.raczynski.com/pn/genrel.htm
More than 120 topics, 300 keywords in the field of computer simulation and modeling. Includes simulation and modeling methods, software tools and general issues. Ideal as an additional text in teaching modeling and simulation. Prepared as a Windows help file. Low cost (US $10) download available.
http://www.raczynski.com/pn/encyk.htm
Different construction with good technical details about loop capacitor and its design.
http://www.qsl.net/mnqrp/Loop/Mag_Loops.htm