> This device modulates the high beam @ some legal
> frequency and some have an option to be only activated
> for 4 seconds when the horn is tapped. Can serve as a
> passing device but has more safety options...
Federal (US DOT) requirements are 4 cps when modulating. The modulated beam
does not have to be the high beam, as I recall. I have a Signal Dynamics
unit and it runs for 2.5 seconds when the horn button is pushed, but only
when the modulator is OFF (at night)....
In fact, here's the whole enchilada:
Title 49 US Code, Sec 571.108
S7.9.4 Motorcycle headlamp modulation system.
S7.9.4.1 A headlamp on a motorcycle may be wired to modulate either the
upper beam or the lower beam from its maximum intensity to a lesser
intensity, provided that:
(a) The rate of modulation shall be 240 <plus-minus> 40 cycles per
minute.
(b) The headlamp shall be operated at maximum power for 50 to 70
percent of each cycle.
(c) The lowest intensity at any test point shall be not less than 17
percent of the maximum intensity measured at the same point.
(d) The modulator switch shall be wired in the power lead of the
beam filament being modulated and not in the ground side of the circuit.
(e) Means shall be provided so that both the lower beam and upper
beam remain operable in the event of a modulator failure.
(f) The system shall include a sensor mounted with the axis of its
sensing element perpendicular to a horizontal plane. Headlamp modulation
shall cease whenever the level of light emitted by a tungsten filament light
operating at 3000 deg. Kelvin is either less than 270 lux (25 foot-candles)
of direct light for upward pointing sensors or less than 60 lux (5.6
foot-candles) of reflected light for downward pointing sensors. The light is
measured by a silicon cell type light meter that is located at the sensor
and pointing in the same direction as the sensor. A Kodak Gray Card (Kodak
R-27) is placed at ground level to simulate the road surface in testing
downward pointing sensors.
(g) When tested in accordance with the test profile shown in Figure
9, the voltage drop across the modulator when the lamp is on at all test
conditions for 12 volt systems and 6 volt systems shall not be greater than
.45 volt. The modulator shall meet all the provisions of the standard after
completion of the test profile shown in Figure 9.
(h) Means shall be provided so that both the lower and upper beam
function at design voltage when the headlamp control switch is in either the
lower or upper beam position when the modulator is off.
S7.9.4.2(a) Each motorcycle headlamp modulator not intended as
original equipment, or its container, shall be labeled with the maximum
wattage, and the minimum wattage appropriate for its use. Additionally,
each such modulator shall comply with S7.9.4.1 (a) through (g) when
connected to a headlamp of the maximum rated power and a headlamp of the
minimum rated power, and shall provide means so that the modulated beam
functions at design voltage when the modulator is off.
(b) Instructions, with a diagram, shall be provided for mounting the
light sensor including location on the motorcycle, distance above the road
surface, and orientation with respect to the light.
