Abstract: There is disclosed a control system for stopping a punch press and comprising first and second proximity sensor-amplifier combinations responsive to the cyclical movements of respective parts of the press to generate respective cyclical signals having respective recurrent digital waveforms which remain invariable while the press and such combinations operate normally. A device responds to a misfeed in the stock strip to change the waveform of the first signal. The two signals are fed to logic circuits which respond either to a change in waveform indicative of such fault or to a change in waveform indicative of malfunction of either combination to produce a signal for stopping the machine.