beam-switching tube[′bēm ‚swich·iŋ ‚tüb]
an electron-beam instrument used for the inertialess switching of low-current electric circuits. Its operation is based on control of the position of an electron beam, which can be directed in a prescribed sequence to different electrodes; the electrodes, functioning as commutator segments, are insulated from one another and are connected to external circuits. The electron-beam current can be controlled by an external signal. Beam-switching tubes have not been widely used. In some cases their functions can be performed by a trochotron.