There are three Sound & Light Units one each at Delhi, Bangalore and Allahabad. The Sound and Light programme, a modified version of Son-et-Lumiere, originated from Europe, is a highly technical medium which is performed on a series of stages spread over a large area. The basic difference between Son-et-Lumiere and the Sound and Light programmes presented by Song & Drama Division is that while the former only narrates the events through Sound track and they are highlighted with appropriate lighting arrangement, in the Sound and Light programmes presented by Song & Drama Division the Sound track is actually enacted by a contingent of artistes consisting of 100 to 120 actors, actrersses and dancers. Unlike Son-et-Lumiere, the Sound and Light programmes of Song & Drama Division are a mobile system which is taken from place to place for a fixed slot of performances. The programme has a component of 25 to 30 technicians also belonging to various disciplines of theatrical productions. This medium is used to educate the masses in general and youth in particular regarding cultural heritage of the country, lives, teachings and philosophy of great personalities and imparting knowledge regarding major historical events through this extremely effective visual medium. Involvement of local artists and technicians ranging between 100 to 120 is one of the most significant aspect of this activity.