ABSTRACT This research article deals with different aspects of redundancy techniques at various levels in complex systems which are helpful in improving reliability. Redundancy is an alternate mean in a system for completing a given operation such that all means must fail before causing a system failure. There are different types of configurations such as series, parallel, series- parallel, parallel- series, k-out-of-n and mixed configurations for a complex system and redundancy can be applied at different levels. In this article an example of a complex system with series configuration is discussed with different types of redundancy techniques at unit level as well as at component level. It is concluded that mixed redundancy technique is best to improve reliability of the system. However, the use of a particular technique of redundancy depends on many factors such as operating characteristics of components or system, weight, size and initial cost etc.