The Laboratory of Dosimetry for Ionizing Radiation at the Institute for Radiological Protection and Nuclear Safety in France is developing an instrumented anthropomorphic dummy to evaluate the effective dose for photon fields in workplaces. This anthropomorphic phantom will be equipped internally with small active detectors at chosen positions. The aim of this paper is to describe the preliminary results of these detectors and their main characteristics. A prototype based on a scintillation detector has been built taking into account the different constraints of our project. The preliminary characterization of the signal measurements and a nontissue equivalence correction method are described.