to the memory cassette 103 is operated under the state where each of the terminals of the connectors is stable in contact therefore stored contents of the memory cassette 103 will be prevented from destruction when the memory cassette is attached or released the second embodiment of a power supply mechanism will be described next with reference to fig1 to fig2 in fig1 and fig1 a connector 104 39 of a memory cassette 103 39 has a notch 109 at the central portion a switch terminal 110 for the memory cassette 103 39 is provided on the portion of the notch 109 the terminal 110 and an adjacent terminal 111 are short circuited in the cassette 103 39 when the connector 104 39 is completely inserted in the connector 102 corresponding terminals 112 and 113 in the connector 102 are short circuited to start the power supply the terminals 110 and 112 are brought into contact after other terminals come in contact stably as shown in fig1 an electric circuit is substantially the same to the circuit of fig1 except that the operation of the switch 15 is replaced by the contact and removement of the terminals 110 and 112 however since the switching operation is done by.