Whether you are shopping for your first shaker system, or just educating yourself to shaker technology in general, you'll find this white paper on Sentek Dynamics shakers helpful. Sentek Dynamics supplies vibration test equipment to reproduce real-world environmental conditions for global manufacturers and offers technology capable of reproducing a wide-variety of test requirements - vibration (sine, random, shock, SoR, RoR, RSTD and others), data recording and dynamic signal analysis.
Although this paper focusses on Sentek Dynamics products, it provides excellent details about shaker technology in general.