The invention relates to a device (3) for detecting and signaling a change in the state of a push button (2), e.g. an emergency-stop button. The device is provided in the form of a add-on that is detachable from the push button (2), and comprises: an electrical energy generator (1) housed in the housing (30) of the device and capable of interacting with a control head (20) of the push button (2) for converting mechanical energy into electrical energy; and a wireless transmitter for transmitting a message to a remote receiver, the wireless transmitter being housed in the housing (30) and electrically connected to the electrical energy generator (1).
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