| 摘要 |
PURPOSE:To ensure that even when only one of a multiplicity of pins is broken, the breakage of the pin is detected securely and speedily, by providing a pressure sensor on the side of a platen against which the tip of a printing pin collides at the time of printing, and a testing means for checking whether a pressure signal due to the collision of the printing pin is generated from the pressure sensor within a predeterined period of time from the time of the generating of a driving signal for the printing pin. CONSTITUTION:When a printing pin strikes a pressure sensor 13 in response to a driving signal from a CPU 1, a pressure signal is generated immediately after the driving signal, and a flip-flop 15 set by the driving signal is immediately reset. After the flip-flop 15 is reset, a test signal is generated. In this case, a discriminating circuit 17 judges that the printing pin is normal When the driving signal from the CPU 1 is applied for a broken printing pin, the pin does not strike the sensor 13, so that no pressure signal is generated. In this case, the circuit 17 judges that the printing pin is broken, and supplies the CPU 1 or other controlling part with a signal indicative of this condition. |
