A communication device adapted to communicate data in contact with a plurality of cartridges, the device comprising: a signal output unit adapted to output a first signal to memories of the plurality of cartridges; a signal reception unit adapted to receive a second signal from the memories of the plurality of cartridges; a plurality of output signal lines adapted to connect the signal output unit with the memories of the plurality of cartridges; a plurality of reception signal lines adapted to connect the signal reception unit with the memories of the plurality of cartridges; a control unit adapted to output a select signal for selecting one of the memories of the plurality of cartridges; switching units adapted to switch connection between the signal output unit and one of the memories of the plurality of cartridges and to establish a connection between one of the memories of the plurality of cartridges and the control unit by connecting said signal output unit via one of said plurality of output signal lines to the one of the memories of the plurality of cartridges in accordance with the select signal output from the control unit; and characterised by a plurality of condensers connected to each of the plurality of output signal lines and each of the plurality of reception signal lines which, when the control unit is connected to a first memory of the memories, cause a first voltage difference between a first output signal line corresponding to the first memory among the plurality of output signal lines and a first reception signal line corresponding to the first memory among the plurality of reception signal lines and a second voltage difference between a second output signal line corresponding to a second memory different from the first memory among the plurality of output signal lines and a second reception signal line corresponding to the second memory among the plurality of reception signal lines such that the first voltage difference is larger than the second voltage difference. a signal output unit adapted to output a first signal to memories of the plurality of cartridges; a signal reception unit adapted to receive a second signal from the memories of the plurality of cartridges; a plurality of output signal lines adapted to connect the signal output unit with the memories of the plurality of cartridges; a plurality of reception signal lines adapted to connect the signal reception unit with the memories of the plurality of cartridges; a control unit adapted to output a select signal for selecting one of the memories of the plurality of cartridges; switching units adapted to switch connection between the signal output unit and one of the memories of the plurality of cartridges and to establish a connection between one of the memories of the plurality of cartridges and the control unit by connecting said signal output unit via one of said plurality of output signal lines to the one of the memories of the plurality of cartridges in accordance with the select signal output from the control unit; and characterised by a plurality of condensers connected to each of the plurality of output signal lines and each of the plurality of reception signal lines which, when the control unit is connected to a first memory of the memories, cause a first voltage difference between a first output signal line corresponding to the first memory among the plurality of output signal lines and a first reception signal line corresponding to the first memory among the plurality of reception signal lines and a second voltage difference between a second output signal line corresponding to a second memory different from the first memory among the plurality of output signal lines and a second reception signal line corresponding to the second memory among the plurality of reception signal lines such that the first voltage difference is larger than the second voltage difference.