We report results from beam tests on silicon microstrip detectors using a binary readout system for ATLAS. The data were collected during the H8 beam test at CERN in August/September 1995 and the KEK test in February 1996. The binary modules tested had been assembled from silicon microstrip detectors of different layout and from front-end electronics chips of different architecture. The efficiency, noise occupancy and position resolution were determined as a function of the threshold setting for various bias voltages and angles of incidence for both irradiated and non-irradiated detectors. In particular, the high spatial resolution of the beam telescope allowed the evaluation of the performance as a function of the track location in between detector strips.