In those days the only reliable vacuum tube was the Western Electric repeater triode,and if one needed a variable resistance he wound a lot of wire on a wooden spool.

• 在那个时候唯一可靠的真空管就是WesternElectric中继器三极管，而如果需要变阻器时，就用金属丝缠在木卷轴上自己做一个。