Power Pentode
The 1S4 vacuum tube is a miniature type used in the
output stage of lightweight, compact, portable,
battery-operated equipment. The 1S4 and 3S4 vacuum tubes
are identical except for the filament arrangement.
They require a miniature 7-contact socket and may be
mounted in any position.
Electrical Data:
Filament Voltage .................... 1.4 DC V
Filament Current ..................... 0.1 A