  We study the general L_0-regular gl(2) spin chain, i.e. a chain where the
sites {i,i+L_0,i+2L_0,...} carry the same arbitrary representation (spin) of
gl(2). The basic example of such chain is obtained for L_0=2, where we recover
the alternating spin chain.
  Firstly, we review different known results about their integrability and
their spectrum. Secondly, we give an interpretation in terms of particles and
conjecture the scattering matrix between them.
