Abstract: A method of synchronizing an equipment unit (200) connected to a communications network (110), the equipment unit being connected to an electrical power supply network (120) providing at least one alternating current power supply voltage (121), the method including the steps of measuring a time difference between the power supply voltage and a synchronization voltage (131), computing a synchronization value, communicating the synchronization value to the equipment unit, the equipment unit detecting the power supply voltage passing through the given state, and synchronizing the equipment unit substantially simultaneously with detecting the supply voltage passing through the given state from the synchronization value. The invention also relates to a synchronization device (300) and a synchronization module (400) used in the synchronization method.