ECLAIRs is a 2D-coded mask imager sensitive from 4 to 250 keV, with a field of view of 80°x 80° and a localization accuracy better than 10', at 7 s. It will deliver triggers by seeking continuously for the appearance of new transient sources in the hard X-ray energy domain, and by determining their localization on the sky. When a new source candidate is detected, an alert will be automatically transmitted to the satellite and to the ground within 1 minute via a VHF network. more...