Transistor single link or a single connection (Richard) a finite element, semi-conductor, the head is just that a bond p-n in there, and like an electronic key action.

three types of transistors, single-linkage, there are:
transistor, single-linkage, in principle, a Elements simple that from a piece of semiconductor n-type, during which a material, semi-conductor, p-type, the penetration given is to be formed. Elements 2N2646 most famous examples of this type.
transistor single link supplement CUJT invert the high state of a material, semi-conductor, p-type, during which a semi-conductor, type n influence is given to the formed. Elements 2N6114 the most famous examples of this type.
the programmable unijunction transistor or put is a multi-connection device, the external resistance show similar features to Richard. This close cousin to the thyristor, and the like, a thyristor consists of four p-n layers. This is a anode and a cathode connected to the first and the last layer, and a gate connected to one of the inner layers. Puts directly interchangeable with conventional UJTs but perform a similar function.