| 摘要 |
<p>In an input circuit which converts a contact signal into a voltage signal, the polarities of voltage signal outputs that correspond to on and off of the contact point change differently depending upon the connection method of the contact point and the current limiting resistor between the power source and the ground. Therefore, non-coincidence is detected between the output voltage signal level and the voltage level at the other end of the current limiting resistor connected to the voltage signal output terminal, in order to obtain voltage signal outputs of which the polarities change in the same manner in response to the on and off of the contact point, irrespective of the above-mentioned connection method. When the circuit thus constructed is to be used large in number, a non-coincidence detecting circuit is provided for each group of divided input circuits, and the voltage signal output of each group of the input circuits is switched and is applied to the non-coincidence detecting circuit. This enables the scale of circuit to be reduced and the number of parts of the circuit to be reduced.</p> |
