One of the key aspects of the upcoming Ultra-Fast Observatory (UFFO) Pathfinder for Gamma-Ray Bursts(GRBs) identification will be the UFFO Burst Alert & Trigger Telescope(UBAT), based on a novel space telescope technique. The UBAT consists of coded mask, hopper, and detector module(DM). The UBAT DM consists of YSO crystal arrays, multi-anode photo mulipliers, and readout electronics. We will present the design and construction of the UBAT DM, and the response of the UBAT DM to X-ray sources.