| 摘要 |
<p>PURPOSE:To detect the disconnection of transmission line from an encoder with a few line numbers by judging the broken transmission line when no current flowing to the transmission line is detected. CONSTITUTION:The circuit 1 supplies a current depending on the ON/OFF of a pulse signal of an encoder to a transmission line 11. The circuit 2 reproduces the different current into an ON/OFF signal. When a current detection circuit 3 detects no current flowing, it is judged that the transmission line 11 is in disconnection. That is, the resistance of a base resistor 32 and a collector resistor 33 of a switching transistor(TR) 31 is selected so that a current flows to a base of the TR 31 even when an output TR 12 of the encoder is switched and a potential of a collector exceeds a threshold voltage of an inverter 34. When the transmission line 11 is in disconnection the TR 31 is turned off because the base potential reaches a Vcc and an output of the inverter 34 changes from a low level to a high level, resulting in indicating the disconnection.</p> |
