PURPOSE: To flow a rotating magnetic field current and a function current only to an objective cassette, illuminate a display lamp for prevention of erroneous pickup and to display the state in operation, by receiving and transmitting a cassette selection signal with the prescribed cassette.

CONSTITUTION: A cassette selection signal is provided for magnetic bubble memory cassettes 91W9n desired to be selected from a cassette control section 8 and a rotating magnetic field current and each function current flow to each cassette only when the cassette selection signal is provided. The cassette selection signal illuminates a light emitting diode provided for each cassette to display a cassette under operation. Since for cassettes not selected and not in operation, no function current and rotating magnetic field current flow, allowing to keep the information surely.