It's the symbol of a current source. There are different symbols used to represent a current source: enter image description here. ... <看更多>

Jul 25, 2019 - Chinese character double happiness in double circle shape. Chinese traditional ornament design, commonly used as a decoration and symbol of ... ... <看更多>

Usually, a double circle means: multi-valued attribute. A double-rectangle means: weak-entity class. ... <看更多>