35a 35b as will be described later when inputted with the analog signal u03b2 the not circuit 62a outputs a digital signal u03c5 as a result the signal u03c5 from the not circuit 62a is outputted to one terminal of the nand circuit 62b the distinction signal u03b1 outputted from the gate array circuit 42 is also inputted to the other terminal of the nand circuit 62b via the line 70 the nand circuit 62b outputs a signal u03b4 to the rank signal terminal 58 of the cpu 43 depending on the state of the distinction signal u03b1 and the signal u03c5 next while referring to the waveform charts shown in fig7 and 9 an explanation will be provided for changes in the waveforms of the analog signal u03b2 and the signals u03c5 and u03b4 resulting from different connection conditions of the switching points 35a 35b fig7 shows waveforms of signals produced when both the switching points 35a 35b provided to the cob 27 are left open fig8 shows waveforms of signals produced when the switching point 35a only is closed fig9 shows waveforms of signals produced when the switching point 35b only is closed when a print head 2 with known rank characteristic is mounted in the printer 1 a distinction signal u03b1 is outputted from the gate array 43 to the driver ic 26 over the print data signal line 59 it should be noted that when the distinction signal u03b1 is outputted over the print data signal line 59 and not over a signal line exclusively for the distinction signal u03b1 other signals such as for driving the print head 2 must not be outputted over the print data signal line 59 at this time resultant current will flow from the.