  In a recent letter, Fisher et al. reported the phenomenon of zero-lag long
range isochronous synchronization via dynamical relaying in systems with delay
[Phys. Rev. Lett. bf 97, 123902 (2006)]. They reported that when one has two
coupled systems A and C, with delay between them, then the introduction of a
third element B between A and C will allow them to synchronize even in regions
of the parameter space where this was not possible without the presence of B.
Here we study in detail the phenomenon and verify that in all the cases studied
(including the ones reported by Fisher et al.) this occurs due to the tendency
of A and B and B and C to be in antiphase synchronization and if A is in
antiphase with B and B is in antiphase with C, it will imply that A and C are
inphase. We show this in coupled quadratic maps, Kuramoto and R\"ossler
oscillators. We also report that there is a simpler configuration where the
same phenomenon occurs and has nearly the same features of the cases studied by
Fisher et al.
