  The first eclipsing binary pulsar, PSR B1957+20, was discovered in 1987.
Since then, 13 other eclipsing low-mass binary pulsars have been found, 12 of
these are in globular clusters. In this paper we list the known eclipsing
binary pulsars and their properties, with special attention to the eclipsing
systems in 47 Tuc. We find that there are two fundamentally different groups of
eclipsing binary pulsars; separated by their companion masses.
  The less massive systems (M_c ~ 0.02 M_sun) are a product of predictable
stellar evolution in binary pulsars. The systems with more massive companions
(M_c ~ 0.2 M_sun) were formed by exchange encounters in globular clusters, and
for that reason are exclusive to those environments. This class of systems can
be used to learn about the neutron star recycling fraction in the globular
clusters actively forming pulsars. We suggest that most of these binary systems
are undetectable at radio wavelengths.
