http://www.commlinx.com.au/schematics.htm : CommLinx Solutions Pty Ltd http://www.uoguelph.ca/~antoon/circ/circuits.htm : Circuits for the Hobbyist http://www.interq.or.jp/japan/se-inoue/e_menu.htm : The hobby of electronic circuit Engineering orhttp://hobby_elec.piclist.com/e_menu.htm http://www.williamson-labs.com/home.htm : Williamson Labs http://www.electronics-lab.com/proj..