Breakdown diode . Unidirectional or bi-directional can be specified .
击穿二极管。可指定单向或双向。
The most common polar pattern is omnidirectional , though unidirectional types may be used to control excessive ambient noise or severe feedback problems .
最普通的指向性为无指向性，尽管指向性类型可以控制过多的环境噪声或严重的啸叫问题。
But the other issue , as clare talwalker , an indian-born anthropologist attached to the centre explained , is that it is increasingly misguided for students to view aid as a unidirectional gift .
