Safety circuit

Now i would like to post something which i came to knew recently from internet resources itself.how does these safety stuffs works, or how does this safety effect lift operation. normally all the companies will do is to connect all the safety in series in order to get a "one input" to the controller to stop the running. and this is the actual thing they wanted. but there is some extension functions also can be provided in this one single series circuit, in the seance of making troubleshooting process fast.and simply that is taping this main circuit at different places and making some named led's to blink while that specific safety has activated.

many companies uses low voltages in their safety circuits and some of them uses a little high(130v ac) voltage for their safety circuits. may be the reason for choosing his little high voltage will be to avoid unnecessary  minor safety notification to the controller such as landing door safety will be activated if a small dust particle came over the contacting parts. so if we provide little high then it may be avoided. And also it will avoid the effet of long safety circuit in the case of high floored lifts