Before revision: This current can then be rectified by a thermionic diode or copper-oxide or selenium rectifier, or by an additional set of mechanical contacts (in which case the vibrator acts as a type of synchronous rectifier).
After revision: This current can then be rectified by a thermionic diode , a copper-oxide / selenium rectifier, or by an additional set of mechanical contacts (in which case the vibrator acts as a type of synchronous rectifier).