A wireless power transfer system including a power transmitter arranged to provide a power transfer to a power receiver via a wireless inductive power transfer signal generated by the power transmitter, wherein: the power receiver is configured to transmit a standby mode exit request to the power transmitter by changing a loading of a communication inductor of the power transmitter, said change of loading causing a change in the impedance of the communication inductor; and the power transmitter comprises: the communication inductor for communicating with the power receiver; a mode controller for controlling the power transmitter to operate in a standby mode wherein a presence of the power receiver is detected but no power transfer signal is generated; a detector for detecting the impedance change of the communication inductor; wherein the mode controller is arranged to initiate a transition from the standby mode to a power transfer mode in response to the detector detecting the impedance change; the system characterized in that the communication inductor is part of a resonance circuit and the detector is arranged to apply an excitation signal causing oscillations to the resonance circuit, and to detect the impedance change from a measurement of at least one of a communication inductor voltage and a communication inductor current; the system further characterized in that the power receiver further comprises a push-button switch, which, when pressed by a user - connects a capacitor (Cmod) that is part of a resonance circuit including a receiver communication inductor (211, Lcom_Rx), or - short-circuits the receiver communication inductor (211, Lcom_Rx), and thereby causes transmission of the standby mode exit request without involving a microcontroller of the power receiver. the power receiver is configured to transmit a standby mode exit request to the power transmitter by changing a loading of a communication inductor of the power transmitter, said change of loading causing a change in the impedance of the communication inductor; and the power transmitter comprises: the communication inductor for communicating with the power receiver; a mode controller for controlling the power transmitter to operate in a standby mode wherein a presence of the power receiver is detected but no power transfer signal is generated; a detector for detecting the impedance change of the communication inductor; wherein the mode controller is arranged to initiate a transition from the standby mode to a power transfer mode in response to the detector detecting the impedance change; the system characterized in that the communication inductor is part of a resonance circuit and the detector is arranged to apply an excitation signal causing oscillations to the resonance circuit, and to detect the impedance change from a measurement of at least one of a communication inductor voltage and a communication inductor current; the system further characterized in that the power receiver further comprises a push-button switch, which, when pressed by a user - connects a capacitor (Cmod) that is part of a resonance circuit including a receiver communication inductor (211, Lcom_Rx), or - short-circuits the receiver communication inductor (211, Lcom_Rx), and thereby causes transmission of the standby mode exit request without involving a microcontroller of the power receiver. the communication inductor for communicating with the power receiver; a mode controller for controlling the power transmitter to operate in a standby mode wherein a presence of the power receiver is detected but no power transfer signal is generated; a detector for detecting the impedance change of the communication inductor; wherein the mode controller is arranged to initiate a transition from the standby mode to a power transfer mode in response to the detector detecting the impedance change; the system characterized in that the communication inductor is part of a resonance circuit and the detector is arranged to apply an excitation signal causing oscillations to the resonance circuit, and to detect the impedance change from a measurement of at least one of a communication inductor voltage and a communication inductor current; the system further characterized in that the power receiver further comprises a push-button switch, which, when pressed by a user - connects a capacitor (Cmod) that is part of a resonance circuit including a receiver communication inductor (211, Lcom_Rx), or - short-circuits the receiver communication inductor (211, Lcom_Rx), - connects a capacitor (Cmod) that is part of a resonance circuit including a receiver communication inductor (211, Lcom_Rx), or - short-circuits the receiver communication inductor (211, Lcom_Rx), and thereby causes transmission of the standby mode exit request without involving a microcontroller of the power receiver.