The zener barrier prevents the transfer of unacceptably high energy from the safe area into the hazardous area. The zener diodes in the zener barrier are connected in thereverse direction. The breakdown voltage of the diodes is not exceeded in normal operation. If this voltage is exceeded, due to a fault in the safe are a the diodes start to conduct, causing the fuse to blow. The zener barrier has a positive polarity, i. E. The anodes of the zener diodes are grounded. The zener barrier is for evaluation of signals from the hazardous area. The diodes of diode return prevent a current into the hazardous are a therefore the current assumption for intrinsic safety calculations is zero.Depending on the application, increased or decreased intrinsic safety parameters apply for serial or parallel connection. For the detailed parameters refer to the ZenerBarrier certificate. Application examples can be found in the system description of the zener Barriers.