1 The BeppoSAX gamma-ray burst monitor

The scientific payload of the Italian-Dutch X-ray astronomy satellite BeppoSAX (Boella et al. 1997) includes a Gamma-Ray Burst Monitor, GRBM (Costa et al. 1998), whose detecting units are the four CsI(Na) scintillators that act primarily as anticoincidence Lateral Shields (LS) for the PDS experiment main detectors (Frontera et al. 1997). Due to their large geometrical area of 1136 cm² each, the LS were also equipped with electronics dedicated to Gamma-Ray Bursts (GRB) detection. The scientific data available from each GRBM detector consist of: 1 s ratemeters continuously stored in the "GRBM" and "AC" energy bands, corresponding, with the actual thresholds settings, to 40-700 and > 100 keV respectively; 240 channels PHA spectra accumulated in the GRBM energy band over a time interval of 128 s; high resolution (down to 0.5 ms) time profiles stored and transmitted when the GRB trigger condition (Costa et al. 1998) is satisfied.