Abstract

This is the first of several papers dealing with the development and description of the signal glass specifications formulated by the Signal Section of the Association of American Railroads in 1935 and 1938. The present paper gives the spectral transmissions of the basic standards—red, yellow, green, blue, purple and lunar white glasses—on which the A. A. R. scale of luminous transmission is based, and defines that scale in fundamental, absolute units. Comparison is made with the scales defined in the 1908 and 1918 signal glass specifications.

© 1939 Optical Society of America

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  1. Standardization of railway signal glasses—Reports on measurements and investigations undertaken by the Colorimetry Section of the National Bureau of Standards at the request of the Signal Section, American Railway Association. Reports Nos. 1 to 5, K. S. Gibson and Geraldine K. Walker; published in Signal Section Proceedings, A. R. A.30, 384 (1933): . The transmission (A. R. A. scale) of 36 specimens of signal glass relative to transmission of 6 A. R. A. standards marked “J. C. Mock 10–3–30,” a report on measurements made at Corning Glass Works, December 9–11, 1930. (June1, 1932.) . Measurements of spectral and luminous transmissions leading to the derivation of new A. R. A. transmissions for the 36 glasses listed in report No. 1. (October24, 1932.) . Spectral and luminous transmissions and derivation of new values of A. R. A. transmission for the 22 “limit” glasses selected by Committee VI, A. R. A., at Corning, November 5–6, 1931 and engraved “J.C.M. 11–6–31.” (December2, 1932.) . Chromaticities and luminous transmissions, with illuminants at 1900°K and 2848°K, for the 22 “limit” glasses described in Report No. 3. (January30, 1933.) . Tentative specifications for railway signal colors. (April27, 1933.) Reports Nos. 6 and 7, K. S. Gibson, Geraldine Walker Haupt, and H. J. Keegan; published in Signal Section Proceedings, A. A. R.36, 136 (1939): . Examination of 65 duplicate limit glasses. (July26, 1934.) . Colorimetric data leading to specification 59–38 for kerosene hand lantern globes; comparison of specifications 59–38, 69–38, and 69–35; certification of duplicate lantern glasses. (September28, 1938.)
  2. A. A. R. Signal Section Specification 69–38, Signal Glasses (exclusive of kerosene hand lantern globes); approved, 1938. The 1935 issue of this specification appeared in that year under the number 69–35. The differences between 69–35 and 69–38 are very slight, and no change at all was made in the transmission scale. The present transmission scale will be considered to have been established in 1935, although the data on which it is based were obtained and reported in 1930–32.
  3. A. A. R. Signal Section Specification 59–38, Kerosene Hand Lantern Globes; approved, 1938. The present A. A. R. scale of transmission is incorporated in Specification 59–38 (so far as applicable) as well as in 69–38. Both specifications 59–38 and 69–38 may be obtained from Mr. R. H. C. Balliet, Secretary, A. A. R. Signal Section, 30 Vesey Street, New York, N. Y.
  4. Proceedings, International Congress on Illumination, Saranac Inn, N. Y., September, 1928, p. 834.
  5. Further information on the early history of railroad signal glass standardization is given in reports by Mock and Gage, Signal Section Proceedings, A. R. A. 30, 373, 377 (1933).
  6. However, the 1908 specification does state that “The manufacturer must submit samples of glasses showing the extreme limits of colors which it is proposed to furnish. These shall bear labels showing the photometric values ….” There were also given in the specification certain qualitative restrictions tending to prevent glass of undesirable color from being used. This original specification is considered further in Section IV, below.
  7. Details of these measurements are given in , Signal Section Proceedings, A. R. A.30, 384 (1933).
  8. Memorandum entitled, Plan for Reexamination and Duplication of A. R. A. Color Standards and Limits now Deposited with Corning Glass Works; this memorandum was prepared by H. P. Gage and represented the conclusions of the subcommittee of Committee VI, A. R. A. Signal Section, meeting at Corning on October 3, 1930.
  9. K. S. Gibson, “Direct-Reading Photoelectric Measurement of Spectral Transmission,” J. Opt. Soc. Am. and Rev. Sci. Inst. 7, 693 (1923); H. J. McNicholas, “Equipment for Routine Spectral Transmission and Reflection Measurements,” Nat. Bur. Stand. J. Research 1, 793 (1928) RP 30; K. S. Gibson, “Spectrophotometry at the Bureau of Standards,” J. Opt. Soc. Am. 21, 564 (1931).
    [Crossref]
  10. Signal Section Proceedings, A. R. A. 30, 390 (1933).
  11. With C2=14,350 micron-degrees. For continuity with the published reports, all values of color temperature in this paper are expressed on this basis. On the color-temperature scale more recently established at the Bureau (H. T. Wensel, D. B. Judd, and W. F. Roeser, Nat. Bur. Stand. J. Research 12, 527 (1934), RP 677), for which C2=14,320, the same energy distribution is given by 2355°K. For values of C2=14,330 (J. F. Skogland, Nat. Bur. Stand. Misc. Pub. No. 86) and 14,360 (H. T. Wensel, “International Temperature Scale and Some Related Physical Constants,” Nat. Bur. Stand. J. Research 22, 375 (1939) RP1189), the respective values of θ are equal to 2357 and 2362.
    [Crossref]
  12. R. Davis and K. S. Gibson, “Filters for the Reproduction of Sunlight and Daylight and the Determination of Color Temperature,” Nat. Bur. Stand. Misc. Pub. No. 114, Table 2 (1931), M 114. However, the values there given do not extend above 720 mμ. Values from 730 to 760 mμ were used as published in Report No. 2.
  13. Proceedings, Sixth Meeting, I. C. I., Geneva, p. 67. These adopted values are those recommended by Gibson and Tyndall (“Visibility of Radiant Energy,” Sci. Pap. Nat. Bur. Stand. 19, 131 (1923), Table 3, S 475) and are incorporated in the so-called 1931 I. C. I. standard observer (Proceedings, Eighth Meeting, I. C. I., Cambridge, p. 19 (1931). D. B. Judd, “The 1931 I. C. I. Standard Observer and Coordinate System for Colorimetry,” J. Opt. Soc. Am. 23, 359 (1933)).
    [Crossref]
  14. H. J. Keegan assisted the authors in these observations.
  15. In the preceding parts of the paper the various transmission scales to which reference is made in the present section have been mostly treated as various versions of the same scale. It is more convenient in this section to consider them as separate scales.
  16. That is, hypothetical glasses having values of TRSA or TAAR=100.0.
  17. Presented at the Ninth Annual Meeting of the Railway Signal Association, Niagara Falls, New York, October 10–12, 1905.
  18. Report of Committee on Colorimetry for 1920–21, L. T. Troland, Chairman, J. Opt. Soc. Am. and Rev. Sci. Inst.6, 527 (1922).
    [Crossref]
  19. Proceedings of the 8th Session, Cambridge, p. 19 (1931).
  20. This will be treated in the next paper.

1934 (1)

With C2=14,350 micron-degrees. For continuity with the published reports, all values of color temperature in this paper are expressed on this basis. On the color-temperature scale more recently established at the Bureau (H. T. Wensel, D. B. Judd, and W. F. Roeser, Nat. Bur. Stand. J. Research 12, 527 (1934), RP 677), for which C2=14,320, the same energy distribution is given by 2355°K. For values of C2=14,330 (J. F. Skogland, Nat. Bur. Stand. Misc. Pub. No. 86) and 14,360 (H. T. Wensel, “International Temperature Scale and Some Related Physical Constants,” Nat. Bur. Stand. J. Research 22, 375 (1939) RP1189), the respective values of θ are equal to 2357 and 2362.
[Crossref]

1933 (2)

Signal Section Proceedings, A. R. A. 30, 390 (1933).

Further information on the early history of railroad signal glass standardization is given in reports by Mock and Gage, Signal Section Proceedings, A. R. A. 30, 373, 377 (1933).

1923 (1)

K. S. Gibson, “Direct-Reading Photoelectric Measurement of Spectral Transmission,” J. Opt. Soc. Am. and Rev. Sci. Inst. 7, 693 (1923); H. J. McNicholas, “Equipment for Routine Spectral Transmission and Reflection Measurements,” Nat. Bur. Stand. J. Research 1, 793 (1928) RP 30; K. S. Gibson, “Spectrophotometry at the Bureau of Standards,” J. Opt. Soc. Am. 21, 564 (1931).
[Crossref]

Davis, R.

R. Davis and K. S. Gibson, “Filters for the Reproduction of Sunlight and Daylight and the Determination of Color Temperature,” Nat. Bur. Stand. Misc. Pub. No. 114, Table 2 (1931), M 114. However, the values there given do not extend above 720 mμ. Values from 730 to 760 mμ were used as published in Report No. 2.

Gage,

Further information on the early history of railroad signal glass standardization is given in reports by Mock and Gage, Signal Section Proceedings, A. R. A. 30, 373, 377 (1933).

Gage, H. P.

Memorandum entitled, Plan for Reexamination and Duplication of A. R. A. Color Standards and Limits now Deposited with Corning Glass Works; this memorandum was prepared by H. P. Gage and represented the conclusions of the subcommittee of Committee VI, A. R. A. Signal Section, meeting at Corning on October 3, 1930.

Gibson, K. S.

K. S. Gibson, “Direct-Reading Photoelectric Measurement of Spectral Transmission,” J. Opt. Soc. Am. and Rev. Sci. Inst. 7, 693 (1923); H. J. McNicholas, “Equipment for Routine Spectral Transmission and Reflection Measurements,” Nat. Bur. Stand. J. Research 1, 793 (1928) RP 30; K. S. Gibson, “Spectrophotometry at the Bureau of Standards,” J. Opt. Soc. Am. 21, 564 (1931).
[Crossref]

Standardization of railway signal glasses—Reports on measurements and investigations undertaken by the Colorimetry Section of the National Bureau of Standards at the request of the Signal Section, American Railway Association. Reports Nos. 1 to 5, K. S. Gibson and Geraldine K. Walker; published in Signal Section Proceedings, A. R. A.30, 384 (1933): . The transmission (A. R. A. scale) of 36 specimens of signal glass relative to transmission of 6 A. R. A. standards marked “J. C. Mock 10–3–30,” a report on measurements made at Corning Glass Works, December 9–11, 1930. (June1, 1932.) . Measurements of spectral and luminous transmissions leading to the derivation of new A. R. A. transmissions for the 36 glasses listed in report No. 1. (October24, 1932.) . Spectral and luminous transmissions and derivation of new values of A. R. A. transmission for the 22 “limit” glasses selected by Committee VI, A. R. A., at Corning, November 5–6, 1931 and engraved “J.C.M. 11–6–31.” (December2, 1932.) . Chromaticities and luminous transmissions, with illuminants at 1900°K and 2848°K, for the 22 “limit” glasses described in Report No. 3. (January30, 1933.) . Tentative specifications for railway signal colors. (April27, 1933.) Reports Nos. 6 and 7, K. S. Gibson, Geraldine Walker Haupt, and H. J. Keegan; published in Signal Section Proceedings, A. A. R.36, 136 (1939): . Examination of 65 duplicate limit glasses. (July26, 1934.) . Colorimetric data leading to specification 59–38 for kerosene hand lantern globes; comparison of specifications 59–38, 69–38, and 69–35; certification of duplicate lantern glasses. (September28, 1938.)

R. Davis and K. S. Gibson, “Filters for the Reproduction of Sunlight and Daylight and the Determination of Color Temperature,” Nat. Bur. Stand. Misc. Pub. No. 114, Table 2 (1931), M 114. However, the values there given do not extend above 720 mμ. Values from 730 to 760 mμ were used as published in Report No. 2.

Judd, D. B.

With C2=14,350 micron-degrees. For continuity with the published reports, all values of color temperature in this paper are expressed on this basis. On the color-temperature scale more recently established at the Bureau (H. T. Wensel, D. B. Judd, and W. F. Roeser, Nat. Bur. Stand. J. Research 12, 527 (1934), RP 677), for which C2=14,320, the same energy distribution is given by 2355°K. For values of C2=14,330 (J. F. Skogland, Nat. Bur. Stand. Misc. Pub. No. 86) and 14,360 (H. T. Wensel, “International Temperature Scale and Some Related Physical Constants,” Nat. Bur. Stand. J. Research 22, 375 (1939) RP1189), the respective values of θ are equal to 2357 and 2362.
[Crossref]

Mock,

Further information on the early history of railroad signal glass standardization is given in reports by Mock and Gage, Signal Section Proceedings, A. R. A. 30, 373, 377 (1933).

Roeser, W. F.

With C2=14,350 micron-degrees. For continuity with the published reports, all values of color temperature in this paper are expressed on this basis. On the color-temperature scale more recently established at the Bureau (H. T. Wensel, D. B. Judd, and W. F. Roeser, Nat. Bur. Stand. J. Research 12, 527 (1934), RP 677), for which C2=14,320, the same energy distribution is given by 2355°K. For values of C2=14,330 (J. F. Skogland, Nat. Bur. Stand. Misc. Pub. No. 86) and 14,360 (H. T. Wensel, “International Temperature Scale and Some Related Physical Constants,” Nat. Bur. Stand. J. Research 22, 375 (1939) RP1189), the respective values of θ are equal to 2357 and 2362.
[Crossref]

Troland, L. T.

Report of Committee on Colorimetry for 1920–21, L. T. Troland, Chairman, J. Opt. Soc. Am. and Rev. Sci. Inst.6, 527 (1922).
[Crossref]

Walker, Geraldine K.

Standardization of railway signal glasses—Reports on measurements and investigations undertaken by the Colorimetry Section of the National Bureau of Standards at the request of the Signal Section, American Railway Association. Reports Nos. 1 to 5, K. S. Gibson and Geraldine K. Walker; published in Signal Section Proceedings, A. R. A.30, 384 (1933): . The transmission (A. R. A. scale) of 36 specimens of signal glass relative to transmission of 6 A. R. A. standards marked “J. C. Mock 10–3–30,” a report on measurements made at Corning Glass Works, December 9–11, 1930. (June1, 1932.) . Measurements of spectral and luminous transmissions leading to the derivation of new A. R. A. transmissions for the 36 glasses listed in report No. 1. (October24, 1932.) . Spectral and luminous transmissions and derivation of new values of A. R. A. transmission for the 22 “limit” glasses selected by Committee VI, A. R. A., at Corning, November 5–6, 1931 and engraved “J.C.M. 11–6–31.” (December2, 1932.) . Chromaticities and luminous transmissions, with illuminants at 1900°K and 2848°K, for the 22 “limit” glasses described in Report No. 3. (January30, 1933.) . Tentative specifications for railway signal colors. (April27, 1933.) Reports Nos. 6 and 7, K. S. Gibson, Geraldine Walker Haupt, and H. J. Keegan; published in Signal Section Proceedings, A. A. R.36, 136 (1939): . Examination of 65 duplicate limit glasses. (July26, 1934.) . Colorimetric data leading to specification 59–38 for kerosene hand lantern globes; comparison of specifications 59–38, 69–38, and 69–35; certification of duplicate lantern glasses. (September28, 1938.)

Wensel, H. T.

With C2=14,350 micron-degrees. For continuity with the published reports, all values of color temperature in this paper are expressed on this basis. On the color-temperature scale more recently established at the Bureau (H. T. Wensel, D. B. Judd, and W. F. Roeser, Nat. Bur. Stand. J. Research 12, 527 (1934), RP 677), for which C2=14,320, the same energy distribution is given by 2355°K. For values of C2=14,330 (J. F. Skogland, Nat. Bur. Stand. Misc. Pub. No. 86) and 14,360 (H. T. Wensel, “International Temperature Scale and Some Related Physical Constants,” Nat. Bur. Stand. J. Research 22, 375 (1939) RP1189), the respective values of θ are equal to 2357 and 2362.
[Crossref]

J. Opt. Soc. Am. and Rev. Sci. Inst. (1)

K. S. Gibson, “Direct-Reading Photoelectric Measurement of Spectral Transmission,” J. Opt. Soc. Am. and Rev. Sci. Inst. 7, 693 (1923); H. J. McNicholas, “Equipment for Routine Spectral Transmission and Reflection Measurements,” Nat. Bur. Stand. J. Research 1, 793 (1928) RP 30; K. S. Gibson, “Spectrophotometry at the Bureau of Standards,” J. Opt. Soc. Am. 21, 564 (1931).
[Crossref]

Nat. Bur. Stand. J. Research (1)

With C2=14,350 micron-degrees. For continuity with the published reports, all values of color temperature in this paper are expressed on this basis. On the color-temperature scale more recently established at the Bureau (H. T. Wensel, D. B. Judd, and W. F. Roeser, Nat. Bur. Stand. J. Research 12, 527 (1934), RP 677), for which C2=14,320, the same energy distribution is given by 2355°K. For values of C2=14,330 (J. F. Skogland, Nat. Bur. Stand. Misc. Pub. No. 86) and 14,360 (H. T. Wensel, “International Temperature Scale and Some Related Physical Constants,” Nat. Bur. Stand. J. Research 22, 375 (1939) RP1189), the respective values of θ are equal to 2357 and 2362.
[Crossref]

Signal Section Proceedings, A. R. A. (2)

Further information on the early history of railroad signal glass standardization is given in reports by Mock and Gage, Signal Section Proceedings, A. R. A. 30, 373, 377 (1933).

Signal Section Proceedings, A. R. A. 30, 390 (1933).

Other (16)

However, the 1908 specification does state that “The manufacturer must submit samples of glasses showing the extreme limits of colors which it is proposed to furnish. These shall bear labels showing the photometric values ….” There were also given in the specification certain qualitative restrictions tending to prevent glass of undesirable color from being used. This original specification is considered further in Section IV, below.

Details of these measurements are given in , Signal Section Proceedings, A. R. A.30, 384 (1933).

Memorandum entitled, Plan for Reexamination and Duplication of A. R. A. Color Standards and Limits now Deposited with Corning Glass Works; this memorandum was prepared by H. P. Gage and represented the conclusions of the subcommittee of Committee VI, A. R. A. Signal Section, meeting at Corning on October 3, 1930.

Standardization of railway signal glasses—Reports on measurements and investigations undertaken by the Colorimetry Section of the National Bureau of Standards at the request of the Signal Section, American Railway Association. Reports Nos. 1 to 5, K. S. Gibson and Geraldine K. Walker; published in Signal Section Proceedings, A. R. A.30, 384 (1933): . The transmission (A. R. A. scale) of 36 specimens of signal glass relative to transmission of 6 A. R. A. standards marked “J. C. Mock 10–3–30,” a report on measurements made at Corning Glass Works, December 9–11, 1930. (June1, 1932.) . Measurements of spectral and luminous transmissions leading to the derivation of new A. R. A. transmissions for the 36 glasses listed in report No. 1. (October24, 1932.) . Spectral and luminous transmissions and derivation of new values of A. R. A. transmission for the 22 “limit” glasses selected by Committee VI, A. R. A., at Corning, November 5–6, 1931 and engraved “J.C.M. 11–6–31.” (December2, 1932.) . Chromaticities and luminous transmissions, with illuminants at 1900°K and 2848°K, for the 22 “limit” glasses described in Report No. 3. (January30, 1933.) . Tentative specifications for railway signal colors. (April27, 1933.) Reports Nos. 6 and 7, K. S. Gibson, Geraldine Walker Haupt, and H. J. Keegan; published in Signal Section Proceedings, A. A. R.36, 136 (1939): . Examination of 65 duplicate limit glasses. (July26, 1934.) . Colorimetric data leading to specification 59–38 for kerosene hand lantern globes; comparison of specifications 59–38, 69–38, and 69–35; certification of duplicate lantern glasses. (September28, 1938.)

A. A. R. Signal Section Specification 69–38, Signal Glasses (exclusive of kerosene hand lantern globes); approved, 1938. The 1935 issue of this specification appeared in that year under the number 69–35. The differences between 69–35 and 69–38 are very slight, and no change at all was made in the transmission scale. The present transmission scale will be considered to have been established in 1935, although the data on which it is based were obtained and reported in 1930–32.

A. A. R. Signal Section Specification 59–38, Kerosene Hand Lantern Globes; approved, 1938. The present A. A. R. scale of transmission is incorporated in Specification 59–38 (so far as applicable) as well as in 69–38. Both specifications 59–38 and 69–38 may be obtained from Mr. R. H. C. Balliet, Secretary, A. A. R. Signal Section, 30 Vesey Street, New York, N. Y.

Proceedings, International Congress on Illumination, Saranac Inn, N. Y., September, 1928, p. 834.

R. Davis and K. S. Gibson, “Filters for the Reproduction of Sunlight and Daylight and the Determination of Color Temperature,” Nat. Bur. Stand. Misc. Pub. No. 114, Table 2 (1931), M 114. However, the values there given do not extend above 720 mμ. Values from 730 to 760 mμ were used as published in Report No. 2.

Proceedings, Sixth Meeting, I. C. I., Geneva, p. 67. These adopted values are those recommended by Gibson and Tyndall (“Visibility of Radiant Energy,” Sci. Pap. Nat. Bur. Stand. 19, 131 (1923), Table 3, S 475) and are incorporated in the so-called 1931 I. C. I. standard observer (Proceedings, Eighth Meeting, I. C. I., Cambridge, p. 19 (1931). D. B. Judd, “The 1931 I. C. I. Standard Observer and Coordinate System for Colorimetry,” J. Opt. Soc. Am. 23, 359 (1933)).
[Crossref]

H. J. Keegan assisted the authors in these observations.

In the preceding parts of the paper the various transmission scales to which reference is made in the present section have been mostly treated as various versions of the same scale. It is more convenient in this section to consider them as separate scales.

That is, hypothetical glasses having values of TRSA or TAAR=100.0.

Presented at the Ninth Annual Meeting of the Railway Signal Association, Niagara Falls, New York, October 10–12, 1905.

Report of Committee on Colorimetry for 1920–21, L. T. Troland, Chairman, J. Opt. Soc. Am. and Rev. Sci. Inst.6, 527 (1922).
[Crossref]

Proceedings of the 8th Session, Cambridge, p. 19 (1931).

This will be treated in the next paper.

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Figures (7)

Fig. 1
Fig. 1

Spectral transmissions defining the scales of luminous transmission for glasses designated as red, as established, respectively, in the 1908 and 1918 specifications of the Railway Signal Association and in the 1935 and 1938 specifications of the Signal Section of the Association of American Railroads. The 1938 specifications, now in effect, are designated as A. A. R. Signal Section Specifications 59–38 and 69–38.

Fig. 2
Fig. 2

Spectral transmissions defining the scales of luminous transmission for glasses designated as yellow, as established, respectively, in the 1908 and 1918 specifications of the Railway Signal Association and in the 1935 and 1938 specifications of the Signal Section of the Association of American Railroads. The 1938 specifications, now in effect, are designated as A. A. R. Signal Section Specifications 59–38 and 69–38.

Fig. 3
Fig. 3

Spectral transmissions defining the scales of luminous transmission for glasses designated as green, as established, respectively, in the 1908 and 1918 specifications of the Railway Signal Association and in the 1935 and 1938 specifications of the Signal Section of the Association of American Railroads. The 1938 specifications, now in effect, are designated as A. A. R. Signal Section Specifications 59–38 and 69–38.

Fig. 4
Fig. 4

Spectral transmissions defining the scales of luminous transmission for glasses designated as blue, as established, respectively, in the 1908 and 1918 specifications of the Railway Signal Association and in the 1935 and 1938 specifications of the Signal Section of the Association of American Railroads. The 1938 specifications, now in effect, are designated as A. A. R. Signal Section Specifications 59–38 and 69–38.

Fig. 5
Fig. 5

Spectral transmissions defining the scales of luminous transmission for glasses designated as purple, as established, respectively, in the 1908 and 1918 specifications of the Railway Signal Association and in the 1935 and 1938 specifications of the Signal Section of the Association of American Railroads. The 1938 specification, now in effect, is designated as A. A. R. Signal Section Specification 69–38.

Fig. 6
Fig. 6

Spectral transmissions defining the scales of luminous transmission for glasses designated as lunar white, as established, respectively, in the 1908 and 1918 specifications of the Railway Signal Association and in the 1935 and 1938 specifications of the Signal Section of the Association of American Railroads. The 1938 specification, now in effect, is designated as A. A. R. Signal Section Specification 69–38.

Fig. 7
Fig. 7

Spectral distribution curves of illuminant at 2360°K and of the light transmitted by the respective B glasses, having values of TAAR close to 100. These curves illustrate the graphical equivalent of the relation defining T2360.

Tables (8)

Tables Icon

Table I Spectral transmissions (percent) of the standard or medium roundels, designated as having a value of TRSA=100; 1908 specification.*

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Table II Spectral transmissions (percent) of the medium roundels, having values of TRSA as indicated; 1918 specification as published.

Tables Icon

Table III Designations of roundels selected in 1930 as the basis of the A. R. A. scale of luminous transmission.

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Table IV Data obtained by one of the authors (K. S. G.) at Corning Glass Works on the glasses selected to replace the former A. R. A. standard roundels.

Tables Icon

Table V Spectral transmissions of the A, B and C glasses (comprising 18 of the 36 glasses listed in Tables IV and VI.

Tables Icon

Table VI Derivation of new A. R. A. transmissions (redefined as A. A. R. transmissions) for the 36 glasses listed in Table IV.

Tables Icon

Table VII Relation between values of TAAR and of T2360, which defines the luminous transmission scale established in the 1935 and 1938 A. A. R. signal glass specifications.

Tables Icon

Table VIII Comparison of values of T2360 computed for values of TRSA=100.0 from the 1918 specification, with similar values for TAAR=100.0 computed from data on which the 1935 specification is based.

Equations (1)

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T θ = Σ E θ V T / Σ E θ V ,