  The aim of the present paper is to analyse the spectrum of Laplace and Dirac
type operators on metric graphs. In particular, we show for equilateral graphs
how the spectrum (up to exceptional eigenvalues) can be described by a natural
generalisation of the discrete Laplace operator on the underlying graph. These
generalised Laplacians are necessary in order to cover general vertex boundary
conditions on the metric graph. In case of the standard (also named
``Kirchhoff'') boundary conditions, the discrete operator is the usual
combinatorial Laplacian.
