  Basic energy requirements of Gamma Ray Burst(GRB) sources can be easily
accounted for by a pair creation process occurring in the "Dyadosphere" of a
Black Hole endowed with an electromagnetic field (abbreviated to EMBH for
"electromagnetic Black Hole"). This includes the recent observations of
GRB971214 by Kulkarni et al. The "Dyadosphere" is defined as the region outside
the horizon of an EMBH where the electromagnetic field exceeds the critical
value for e^+ e^- pair production. In a very short time $\sim O(hbar mc^2}),
very large numbers of pairs are created there. Further evolution then leads
naturally to a relativistically expanding pair-electromagnetic-pulse
(PEM-pulse). Specific examples of Dyadosphere parameters are given for 10 and
10^5 solar mass EMBH's. This process does occur for EMBH with charge-to-mass
ratio larger than 2.210^{-5} and strictly smaller than one. From a fundamental
point of view, this process represents the first mechanism proved capable of
extracting large amounts of energy from a Black Hole with an extremely high
efficiency (close to 100%).
