Multiwire drift chambers are well known devices, widely used with good energy resolution and building principles that are relatively simple. The detection of fluorescence radiation with such detector is subordinated to capacities to discriminate the signal of interest from the background. This operation can be performed introducing a window discriminator stage in the read-out electronics (after the preamplification and filtering stages). A high-speed window discriminator implemented with ECL logic level is designed to trigger the data acquisition system of a position-sensitive multiwire chamber. The discriminator consists of an analogous part and a digital part. The main idea is processing with two different comparators the input signal of the discriminator - one for the low and one for the high threshold - and then using a logic circuit to decide if the original input signal is or not in the window requested. The analogous components of the discriminator have variable thresholds and output pulse widths as well as some options for high rates in the chamber. The digital components produce standard logic signals and keep real time information in the meanwhile. Measurements are performed to test such device. In particular, linearity, efficiency measurements (up to 10 MHz) and test results to evaluate the resolution in terms of amplitude of the input signal, will be presented in this work.