http://peer.berkeley.edu/laboratories/shaking_table.html
                                 http://www.curee.org/
                                 http://nees.org/resources/2738

                                 Quanser Shake Table. http://quanser.blogspot.com.es/2013/02/how-quanser-shake-tables-are-shaking-up.html
                                 Desktop Shake Table. http://tdgtestbox.blogspot.com.es/2012/04/desktop-shake-table-for-educational.html
                                 Example 1. http://www.exo.net/~donr/activities/Shake_Table.pdf
                                 Example 2. http://www.geo.mtu.edu/~jdiehl/ETM.pdf
                                 Example 3. http://mceer.buffalo.edu/infoservice/Education/shaketableLessonPlan.asp

                                 http://electronicdesign.com/test-amp-measurement/low-cost-function-generator
                                 http://www.ecs.umass.edu/ece212/ECE212_lab6.pdf
                                 https://www.sparkfun.com/products/9002
                                 http://www.instructables.com/id/Analogue-Function-Generator/
                                 http://www.myplace.nu/avr/minidds/index.htm
                                 http://interface.khm.de/index.php/lab/experiments/arduino-dds-sinewave-generator/