using discharge tubes only

Full Title

Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases > without intermediate conversion into DC > by static converters (controlling transformers, reactors or choke coils, e.g. by tap changing H02P13/00) > using discharge tubes with control electrode or semiconductor devices with control electrode > using devices of a triode or transistor type requiring continuous application of a control signal > using discharge tubes only