Abstract: A device for detecting alternating voltage includes input terminals for the application of an alternating voltage to be detected and output terminals, at which application of the alternating voltage is indicated. The input terminals and the output terminals are galvanically separated from each other by a coupler. A control element of the coupler is supplied with operating current from the applied alternating voltage, and a switching element of the coupler is connected to the output terminals. The device is characterized by a zero-crossing detector for the alternating voltage to be detected, which zero-crossing detector supplies the control element of the coupler with the operating current in pulses. A method for detecting alternating voltage is obtained through use of the device.