【电】 单向微音器

麦克风指向性:麦克风背有有气孔的,就是有指向性或抗噪型的麦克风,完全密封的,就是全指向的麦克风.

directional selection

solenoid directional valve

error in bearing (tuning error, directional error)

directional response

down hole deviation drilling (directional drilling)

directional gyroscope【航】;gyrocompass【航】;gyroscopic compass【航】

directional supplementation and drainage

three tower directional antenna