According to the reverberation model for broad emission line variability in active galactic nuclei, the emission-line luminosity at a given epoch may be expressed formally as the convolution of the input ionizing continuum light curve with a transfer function, the form of which depends on the properties of the emitting material. The transfer functions for several simple models of the broad-line region characterized by various geometrical configurations and velocity fields are calculated. How the structure of the transfer function is related to the model parameters is discussed and thereby show how several important properties of the emitting region, such as its size, geometry, emissivity distribution and velocity field, may be inferred.