| 摘要 |
A plurality of sheet feed units 11, 12 , . . . have the same circuit structure with each other. One ends of sensors 113 through 116 which detect whether there is a sheet and the size of the sheet are connected in parallel with sensors which are disposed to other units via communication lines, and also with input ports of a CPU 101 of a main printer section 10 . On the other hand, the other ends of the sensors are connected with a transistor 103 a which is disposed to the main printer section 10 . For instance, as the CPU 101 switches a port SELL to the H level, the transistor 103 a turns on and voltages at the input ports of the CPU 101 change in accordance with the states of the sensors 113 through 116 , i.e., the state of sheet feed unit 11.
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