Električne sheme
http://www.ee.washington.edu/circuit_archive/circuits/
http://www.duncanamps.com/
http://users.otenet.gr/~athsam/
http://www.inet.hr/~obacan/sheme.htm
http://www.aaroncake.net/circuits/
http://www.zen22142.zen.co.uk/schematics.htm
http://www.next.gr/
http://www.circuit-finder.com/
http://www.radiolocman.com/
http://www.damir-pavkovic.iz.hr/sheme/tel/133-adsl-spliter.html
http://www.drtube.com/audioamp.htm
http://www.eserviceinfo.com/
http://www.epanorama.net/index.php?index=circuit
http://www.repairfaq.org/sam/sambook.htm