Patent ID: 7555353
Filing Date: 2009-06-30
Classification: G05B

Abstract:
1. A safety slave unit that with a plurality of input devices based on a safety specification and activated when a danger exists connected thereto, receives input signals about the presence or absence of activation from the input devices, and is connected to a safety controller based on the safety specification through a network so as to transmit the input signals to a communication master of the safety controller, comprising: an input terminal portion having a plurality of input terminals for receiving the input signals from said input devices; an error diagnostic portion that diagnoses an error of breaking or short circuit of wirings between each of said plurality of input terminals and said input devices, and sets a logical value “High” as a diagnosis status data upon the absence of the error and sets a logical value “Low” upon the presence of the error; and a processing means that forces to change the logical value of an actual input signal representing the presence or absence of activation received from each of said input terminals to a logical value corresponding to the presence of activation when the diagnosis status data of the input terminal corresponding to said actual input signal is a logical Low, allows the logical value of an actual input signal to remain when the diagnosis status data of the input terminal corresponding to said actual input signal is a logical High, and transmits to said communication master of said safety controller a pair of said logical values of the actual input signal and the corresponding diagnosis status data wherein the logical value of said actual input signal is regarded as a logical value of a control data of each of the corresponding input devices.