Answer: triodes

AnswerCrossword Clue
TRIODES

Some vacuum tubes

TRIODES

Old TV tubes

TRIODES

Tubes in old TVs

TRIODES
Vacuum tubes
TRIODES
Electron tubes
TRIODESVacuum tubes containing three elements
TRIODESCertain electron tubes
TRIODESSome old TV tubes
TRIODESSome tubes