Interpretation ID: nht87-3.38

TYPE: INTERPRETATION-NHTSA

DATE: 12/07/87

FROM: RICHARD H. SCHULTZ -- AMERICAN PULSE LIGHTS INC

TO: ROBERT J. KNAUFF

TITLE: NONE

ATTACHMT: ATTACHED TO LETTER DATED 07/24/89 FROM STEPHEN P. WOOD -- NHTSA TO ROBERT KNAUFF; REDBOOK A33; FMVSS 108; LETTER DATED 06/08/89 FROM ROBERT J. KNAUFF -- APPLIED RESEARCH AND DESIGN INC TO KATHLEEN DEMETER -- DOT; LETTER DATED 08/16/88 FROM RICH ARD H. SCHULTZ -- AMERICAN PULSE LIGHTS INC TO ROBERT KNAUFF

TEXT: Dear Mr. Knauff:

It was good to hear from you today and I'm glad that you are proceeding in a proper manner regarding the single-pulse signal enhancement feature that you propose to market for use in certain stop signal lamps.

As we discussed, there should be no intensity problem with the use in W, W2 and W3 types because there is no maximum intensity written into the standards for those lamp types. The lamp design intensities also generally far exceed what the three "W" stan dards call for, so any masking of the reflector in the lamp by the photo tube should not prevent adequate performance.

The flash energy formula described in SAE J1318 APR86 (S2.11) may be used to determine compliance with the maximum intensity requirement of SAE "U" type supplementary stop lamps. In J1318, class 1 directional lamps (table8) require 50 candela-seconds of flash energy at H-V. The same functions type lamp and test location in SAE J595 AUG83 (table 1) requires 300 cd intensity. This is a ratio of 1:6. It therefore follows that the maximum from flash energy in an SAE "U" type with a 60 cd limit should be 10 candela-seconds.

When you can obtain a test report that indicates the candela-seconds in an SAE "U" lamp, I would like to see a demonstration of the tested arrangement for assurance that there is no "discomfort" glare at that level. This is primarily because we have a t otally new concept here and we want to be on the safe side. Same goes for use in school bus type "W2" lamps. The momentary light will be paler than the limit for red specified in SAE J578d color standard, but if it is not within the limit for white, it will be an acceptable color.

You said that there is no problem with setting higher or lower intensities if necessary, so you should be able to proceed with your formal request for authorization after the test and demonstration go as anticipated.

Sincerely,