Gain Notes for Revolution 261 JEM-X1: A quite ordinary revolution with fine gain smoothing. All data from this revolution should be useable. The first two points of each data set are the partial switch-on with the High Voltage 3 steps below its nominal value. In a couple of cases the hook that appears at the beginning of the revolution where fast and slow relaxation effects compete, the down swing of the hook is not well fitted, so users are well advised to be cautious using spectral data from this settling period. This caveat however, applies to all JEM-X data, even where gain smoothing functions perfectly, because it cannot be estimated to what extent the four calibration sources reflect the settling occurring all over the microstrip plate. CAO 18/11/2005