A low‐energy x‐ray detection system has been developed and used on two sounding rocket flights. Proportional counters, sensitive to x rays with quantum energies between 2 and 30 keV, are used in this system. The signals from these counters are modified so that they can be telemetered with an FM‐FM system in such a way that the pulse amplitude is preserved. Pulse‐height analysis is done at the ground station. With this simple system, it is possible to obtain spectra of cosmic x‐ray sources limited only by the resolution of the detectors.