A dynamic flip-flop includes a first input latch coupled to receive a data input signal and a second input latch coupled to receive the complement of the data input signal. The chambers are filled with an electrorheological fluid and are connected to one another via an annular gap-like overflow channel. The apparatus casing comprises a first and a second side casing counterpart hinged together to allow its opening and closure. The input circuit produces, in response to the voltage signal, either a first signal or a first circuit condition at the output terminal of the input circuit, representative of the changing current in the power cable. The artificial snow-making devices have discharge nozzles oriented to project the artificial snow away from the vessel onto or above the water adjacent the vessel. , without a connection being made to the calling party.