The Russian 5C4M (5ц4М) is an example of a typical high current rectifier for small equipment use. It is indirectly heated but the cathode is tied to one side of the heater. The OTK mark indicates that it was made for military use. The datasheet indicates that the 5Y3GB is equiva-lent. The wide glass tube envelope is 28mm in diameter and, excluding the IO base pins, is 65mm tall.