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⑴ Resistor-protected safety barrier: The principle of a resistor-protected safety barrier involves the use of a current-limiting resistor R2 to restrict the output current so that it meets the requirements for intrinsically safe operation. Voltage-limiting components D1 and D2 are used to limit the output voltage, when the safety barrier is operating normally. Neither D1 nor D2 is conductive. When a fault occurs in the safety barrier, for example if the non-intrinsic input terminal experiences a voltage increase that exceeds the normal operating voltage and reaches the conduction voltage of D1 or D2, then either D1 or D2 will become conductive, thereby limiting the voltage within its regulated range. As long as D1 and D2 remain undamaged, the voltage at the intrinsic output terminal will not rise, ensuring that it stays within the regulated range set by D1 or D2. The R0 resistor allows a large current to flow through D1 and D2, thereby serving as a protection element for these voltage stabilizing diodes. The value of R1 is very small; it is used to determine whether D1 or D2 has failed during operation of the safety barrier. www.273cn.com – Signal isolators; www.chinafb123.com – Safety barriers. (2) Fuse-protected safety barriers: The principle of these safety barriers is similar to that of those with resistance protection, except that the R0 resistor is replaced by an RF fuse, thereby providing more reliable and secure protection. www.jjksmz.com – Health pillows; www.gouwenr.net – Solutions against canine distemper; www.ggjjzx.net – Canine distemper; China Massage/ www.chinadfree.com