vacuum-tube keying

vacuum-tube keying

[′vak·yəm ¦tüb ′kē·iŋ]
(electronics)
Code-transmitter keying system in which a vacuum tube is connected in series with the plate supply lead of a frequency-controlling stage of the transmitter; when the key is open, the tube blocks, interrupting the plate supply to the output stage; closing the key allows the plate current to flow through the keying tube and the output tubes.