These are electronic series spring clamp double level Terminal Blocks with built in diodes and LED. The built in diode acts as a free wheeling diode which is connected across the inductive load such as relay coils, solenoid valves, contactor coils to eliminate or suppress sudden voltage spike which appears across the load when its supply voltage is removed. CXDL2.5(E)LD1 Terminal Block has a built in LED circuit for online indication. CX2.5/4(E)D1 is specially designed 4 wire spring clamp Terminal Block with a built in diode. This Terminal has a built in 1N4007 diode for reverse polarity protection and also allows uni directional flow of current.