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Transistors have certain characteristics which are not present in vacuum tubes. Some of these characteristics may be best classified as symmetrical properties. The first kind of symmetry may be found in the complementary characteristics of the n-p-n and p-n-p transistors. Circuits using both kinds of transistors in combination provide unique advantages in reduction of components and other circuit simplifications. A second kind of symmetry is displayed by single units since the emitter and collector may be interchanged. This symmetry permits a current flow of either direction controlled alike by the base current. This basic property is useful in switching circuits for clamping, phase and frequency comparison, modulation, and so forth. A high efficiency deflection-current circuit for television was developed using this principle.