The H1 lamp uses a P14.5s base in accord with IEC 60061.
This is a round metal prefocus base 14.5mm in diameter with a flat and two dimples so the H1 can be installed in a lamp only
in the one correct orientation. There is one 6.35mm male spade terminal in the centre of the base,
through which power is supplied. The H1 grounds through the metal base itself.
Power and output
Under ECE Regulation 37, which governs automotive filament lamps in most of the world,
the H1 lamp's nominal rating is 55 watts at 12 volts, and its test rating is 68W (maximum) and 1550 ±15% lumens at 13.2V.
R37 also contains provisions for 6-volt, 55-watt and 24-volt, 70-watt H1 lamps.
The United States government does not recognise ECE regulations, but rather applies its own regulations.
Under these, the H1 is rated 65W (maximum) and 1410 lumens ±15% at 12.8V.
Despite the two different sets of specified voltages and test protocols, the lamps themselves are the same;
with few exceptions, 12-volt H1 lamps are generally manufactured and tested to comply with both regulations.
Colour of light
Under ECE regulations, H1 lamps are required to emit white or selective yellow light.U.S. regulations require H1 lamps
to emit white light. Under both ECE and U.S. specifications, the allowable range of white light is quite large;
some H1 lamps have a slight blue or yellow tint to the glass yet still produce light legally acceptable under the
requirement for white light.