This is a standard of the Japan Electronics and Information Technology Industries Association (JEITA). It covers low voltage and has both current and voltage ratings. It is also referred to as a jack, plug, or receptacle.
EIAJ Standard 1/2/3

PL04A(EIAJ-1)
A (Outline):2.35mm
B (Inner Diameter):0.7mm
C:9.5mm
PL04B(EIAJ-2)
A (Outline):4mm
B (Inner Diameter):1.7mm
C:9.5mm
PLO4C(EIAJ-3)
A (Outline):4.75mm
B (Inner Diameter):1.7mm
C:9.5mm