Crystal detector (English Wikipedia)

Phillips, Vivian J. (1980). Early Radio Wave Detectors. London: Inst. of Electrical Engineers. pp. 18–21. ISBN 978-0906048245.
Phillips, Vivian J. (1980). Early Radio Wave Detectors. London: Inst. of Electrical Engineers. pp. 205–209, 212. ISBN 978-0906048245.
Sarkar, Tapan K.; Sengupta, Dipak L. "An appreciation of J. C. Bose's pioneering work in millimeter and microwaves" in Sarkar, T. K.; Mailloux, Robert; Oliner, Arthur A. (2006). History of Wireless. John Wiley and Sons. pp. 295–296, 301–305. ISBN 978-0471783015.
Sarkar, et al (2006) History of Wireless, pp. 477–483
The 1913 edition of the US Navy's manual of radio stated: "Only one type of detector is now in use: the crystal. Coherers and microphones are practically obsolete, and comparatively few magnetic and Audion or valve [triode] detectors have been installed."Phillips, Vivian J. (1980). Early Radio Wave Detectors. London: Inst. of Electrical Engineers. pp. 212. ISBN 978-0906048245.
The 1920 "British Admiralty Handbook of Wireless Telegraphy" stated that: "Crystal detectors are being replaced by [triode] valve detectors which are more stable, easier to adjust, and generally more satisfactory". The 1925 edition said valves were "replacing the crystal for all ordinary purposes" Phillips, Vivian J. (1980). Early Radio Wave Detectors. London: Institute of Electrical Engineers. pp. 212. ISBN 978-0906048245.

arlingtoncemetery.net

Some biographical information on General Henry H.C. Dunwoody is available at Arlington National Cemetery.

books.google.com

Basalla, George (1988). The Evolution of Technology. UK: Cambridge University Press. pp. 44–45. ISBN 978-0-521-29681-6.
Braun, Agnès; Braun, Ernest; MacDonald, Stuart (1982). Revolution in Miniature: The History and Impact of Semiconductor Electronics. Cambridge University Press. pp. 11–12. ISBN 978-0521289030.
Sievers, Maurice L. (1995). Crystal Clear: Vintage American Crystal Sets, Crystal Detectors, and Crystals, Vol. 1. Sonoran Publishing. pp. 3–5. ISBN 978-1886606012.
Hickman, Ian (1999). Analog Electronics. Newnes. p. 46. ISBN 978-0750644167.
Lee, Thomas H. (2004). Planar Microwave Engineering: A Practical Guide to Theory, Measurement, and Circuits, Vol. 1. Cambridge University Press. pp. 4–9, 297–300. ISBN 978-0521835268.
Orton, John W. (2004). The Story of Semiconductors. Oxford University Press. pp. 20–23. ISBN 978-0198530831.
Seitz, Frederick; Einspruch, Norman (4 May 1998). The Tangled History of Silicon in Electronics. Silicon Materials Science and Technology: Proceedings of the Eighth International Symposium on Silicon Materials Science and Technology, Vol. 1. San Diego: The Electrochemical Society. pp. 73–74. ISBN 9781566771931. Retrieved 27 June 2018.
Lee, Thomas H. (2004). Planar Microwave Engineering: A Practical Guide to Theory, Measurement, and Circuits, Vol. 1. Cambridge University Press. pp. 4–5. ISBN 978-0521835268.
Riordan, Michael; Lillian Hoddeson (1988). Crystal fire: the invention of the transistor and the birth of the information age. USA: W. W. Norton & Company. pp. 19–21, 92. ISBN 978-0-393-31851-7.
Winston, Brian (2016). Misunderstanding Media. Routledge. pp. 256–259. ISBN 978-1315512198.
Sterling, Christopher H.; O'Del, Cary (2010). The Concise Encyclopedia of American Radio. Routledge. pp. 199–201. ISBN 978-1135176846.
"...crystal detectors have been used [in receivers] in greater numbers than any other [type of detector] since about 1907." Marriott, Robert H. (September 17, 1915). "United States Radio Development". Proceedings of the Institute of Radio Engineers. 5 (3): 184. doi:10.1109/jrproc.1917.217311. S2CID 51644366. Retrieved 2010-01-19.
US National Bureau of Standards (March 1918). Circular No. 74: Radio Instruments and Measurements. Washington DC: United States Government Printing Office. p. 105.
The Principles Underlying Radio Communication, 2nd Ed. (Radio communication pamphlet no. 40). Written by the US Bureau of Standards for the US Army Signal Corps. 1922. pp. 433–439.
Bucher, Elmer Eustice (1920). The Wireless Experimenters Manual. New York: Wireless Press. p. 167.
Hirsch, William Crawford (June 1922). "Radio Apparatus - What is it made of?". The Electrical Record. 31 (6): 393–394. Retrieved 10 July 2018.
Cockaday, Laurence M. (1922). Radio-telephony for Everyone. New York: Frederick A. Stokes Co. p. 94.
Stanley, Rupert (1919). Textbook of Wireless Telegraphy Volume 1: General theory and practice. London: Longmans, Green and Co. pp. 311–318.
Lescarboura, Austin C. (1922). Radio for Everybody. New York: Scientific American Publishing Co. pp. 144–146.
Bucher, Elmer Eustice (1920). The Wireless Experimenter's Manual. Wireless Press. p. 164.
Morgan, Alfred Powell (1914). Wireless Telegraph Construction for Amateurs, 3rd Ed. New York: D. Van Nostrand Co. pp. 198–199.
Edelman, Phillip E. (1920). Experimental Wireless Stations. New York: Norman W. Henly Publishing Co. pp. 258–259.
Cole, Arthur B. (1913). The Operation of Wireless Telegraph Apparatus. New York: Cole and Morgan. p. 15.
Sievers, Maurice L. (2008). Crystal Clear: Vintage American Crystal Sets, Crystal Detectors, and Crystals. Sonoran Publishing. p. 6. ISBN 978-1-886606-01-2.
Collins, Archie Frederick (16 March 1907). "Carborundum and silicon detectors for wireless telegraphy". Scientific American. 96 (11). Munn and Co.: 234. doi:10.1038/scientificamerican03161907-234. Retrieved 31 July 2020.
Bucher, Elmer Eustice (1921). Practical Wireless Telegraphy: A Complete Text Book for Students of Radio Communication. New York: Wireless Press, Inc. pp. 135, 139–140.
Pierce, George Washington (1910). Principles of Wireless Telegraphy. New York: McGraw-Hill Book Co. pp. 160–162.
Aitken, Hugh G.J. (2014). The Continuous Wave: Technology and American Radio, 1900-1932. Princeton University Press. pp. 4–7, 32–33. ISBN 978-1400854608.
Braun, F. (1874), "Ueber die Stromleitung durch Schwefelmetalle" [On current conduction through metal sulfides], Annalen der Physik und Chemie (in German), 153 (4): 556–563, Bibcode:1875AnP...229..556B, doi:10.1002/andp.18752291207
Pierce, George W. (July 1907). "Crystal rectifiers for electric currents and electric oscillations, Part 1: Carborundum". Physical Review. 25 (1): 31–60. Bibcode:1907PhRvI..25...31P. doi:10.1103/physrevseriesi.25.31. Retrieved 25 July 2018.
Roer, T.G. (2012). Microwave Electronic Devices. Springer Science and Business Media. pp. 5–7. ISBN 978-1461525004.
The 1911 edition of the US Navy's manual of radio stated: "There are but two types of detectors now in use: crystal or rectifying detectors and the electrolytic. Coherers and microphones [another type of coherer detector] are practically obsolete, and comparatively few of the magnetic and Audion or valve [triode] detectors have been installed."Robison, Samuel Shelburne (1911). Manual of Wireless Telegraphy for the Use of Naval Electricians, 2nd Ed. Washington DC: United States Naval Institute. p. 128.
Marconi used carborundum detectors beginning around 1907 in his first commercial transatlantic wireless link between Newfoundland, Canada and Clifton, Ireland. Beauchamp, Ken (2001). History of Telegraphy. Institution of Electrical Engineers. p. 191. ISBN 978-0852967928.
Grebennikov, Andrei (2011). RF and Microwave Transmitter Design. John Wiley & Sons. p. 4. ISBN 978-0470520994. Archived from the original on 2016-09-17.
Ben-Menahem, Ari (2009). Historical Encyclopedia of Natural and Mathematical Sciences, Vol. 1. Springer. p. 3588. ISBN 978-3540688310. Archived from the original on 2017-11-23.
Lee, Thomas H. (2004) The Design of CMOS Radio-Frequency Integrated Circuits, 2nd Ed., p. 20
Gernsback, Hugo (September 1924). "A Sensational Radio Invention". Radio News: 291. and "The Crystodyne Principle", Radio News, September 1924, pages 294-295, 431.
Round, Henry J. (9 February 1907). "A note on carborundum". Electrical World. 49 (6): 309. Retrieved September 1, 2014.
Schubert, E. Fred (2003). Light-emitting Diodes. Cambridge University Press. pp. 2–3. ISBN 978-0521533515.
Graham, Loren (2013). Lonely Ideas: Can Russia Compete?. MIT Press. pp. 62–63. ISBN 978-0262019798.
The 1918 edition of the US Navy's manual of radio stated: "There are two types of detectors now in use: the Audion [triode] and the crystal or rectifying detector. Coherers and microphones [another type of coherer detector] are practically obsolete... but the use of Audions...is increasing."Robison, Samuel Shelburne (1918). Manual of Wireless Telegraphy for the Use of Naval Electricians, 4th Ed. Washington DC: United States Naval Institute. p. 156.
Michael Riordan, Lillian Hoddeson (1998) Crystal Fire: The Invention of the Transistor and the Birth of the Information Age, p. 89-93
Mott, Neville F. (1 May 1939). "The theory of crystal rectifiers". Proceedings of the Royal Society of London, Series A. 171 (944): 27–38. Bibcode:1939RSPSA.171...27M. doi:10.1098/rspa.1939.0051. JSTOR 97313. Retrieved 3 August 2018. reprinted in Alexandrov, A. S. (1995). Sir Neville Mott: 65 Years in Physics. World Scientific. pp. 153–179. ISBN 978-9810222529.

britannica.com

"Greenleaf Whittier Pickard". Encyclopaedia Britannica online. Encyclopaedia Britannica Inc. 2018. Retrieved 31 July 2018.

bsu.edu

cardinalscholar.bsu.edu

Craddock, Christine D. (24 March 1987). "Crystal Radio: An historical survey" (PDF). Honors Thesis. Ball State University, Muncie, Indiana. Retrieved 2 August 2018.

computerhistory.org

"1931: "The Theory Of Electronic Semi-Conductors" is Published". The Silicon Engine. Computer History Museum. 2018. Retrieved 1 August 2018.

cornell.edu

djena.engineering.cornell.edu

Lukasiak, Lidia; Jakubowski, Andrzej (January 2010). "History of Semiconductors" (PDF). Journal of Telecommunications and Information Technology. ISSN 1509-4553. Retrieved 2 August 2018.

crystalradio.net

Douglas, Alan (April 1981). "The Crystal Detector". IEEE Spectrum. 18 (4): 64–69. doi:10.1109/MSPEC.1981.6369482. hdl:10366/158938. ISSN 0018-9235. S2CID 44288637. archived: part1, part2, part3, part4

doi.org

Douglas, Alan (April 1981). "The Crystal Detector". IEEE Spectrum. 18 (4): 64–69. doi:10.1109/MSPEC.1981.6369482. hdl:10366/158938. ISSN 0018-9235. S2CID 44288637. archived: part1, part2, part3, part4
"...crystal detectors have been used [in receivers] in greater numbers than any other [type of detector] since about 1907." Marriott, Robert H. (September 17, 1915). "United States Radio Development". Proceedings of the Institute of Radio Engineers. 5 (3): 184. doi:10.1109/jrproc.1917.217311. S2CID 51644366. Retrieved 2010-01-19.
Collins, Archie Frederick (16 March 1907). "Carborundum and silicon detectors for wireless telegraphy". Scientific American. 96 (11). Munn and Co.: 234. doi:10.1038/scientificamerican03161907-234. Retrieved 31 July 2020.
Braun, F. (1874), "Ueber die Stromleitung durch Schwefelmetalle" [On current conduction through metal sulfides], Annalen der Physik und Chemie (in German), 153 (4): 556–563, Bibcode:1875AnP...229..556B, doi:10.1002/andp.18752291207
Pierce, George W. (July 1907). "Crystal rectifiers for electric currents and electric oscillations, Part 1: Carborundum". Physical Review. 25 (1): 31–60. Bibcode:1907PhRvI..25...31P. doi:10.1103/physrevseriesi.25.31. Retrieved 25 July 2018.
Emerson, D. T. (December 1997). "The work of Jagadish Chandra Bose: 100 years of mm-wave research". IEEE Transactions on Microwave Theory and Techniques. 45 (12): 2267–2273. Bibcode:1997ITMTT..45.2267E. doi:10.1109/22.643830. Retrieved 29 July 2018. also reprinted on IndianDefense Archived 2018-08-09 at the Wayback Machine
Bose, Jagadish Chandra (January 1899). "On electric touch and the molecular changes produced in matter by electric waves". Proceedings of the Royal Society of London. 66 (424–433): 452–474. Bibcode:1899RSPS...66..452C. doi:10.1098/rspl.1899.0124. S2CID 121203904.
Zheludev, Nikolay (April 2007). "The life and times of the LED – a 100-year history" (PDF). Nature Photonics. 1 (4): 189–192. Bibcode:2007NaPho...1..189Z. doi:10.1038/nphoton.2007.34. Archived from the original (PDF) on 2017-03-31. Retrieved 2007-04-11.
Losev, O. V. (1927). "Светящийся карборундовый детектор и детектирование с кристаллами" [Luminous carborundum detector and detection with crystals]. Телеграфия и Телефония без Проводов (Wireless Telegraphy and Telephony). 5 (44): 485–494. English version published as Lossev, O. V. (November 1928). "Luminous carborundum detector and detection effect and oscillations with crystals". Philosophical Magazine. Series 7. 5 (39): 1024–1044. doi:10.1080/14786441108564683.
Mott, Neville F. (1 May 1939). "The theory of crystal rectifiers". Proceedings of the Royal Society of London, Series A. 171 (944): 27–38. Bibcode:1939RSPSA.171...27M. doi:10.1098/rspa.1939.0051. JSTOR 97313. Retrieved 3 August 2018. reprinted in Alexandrov, A. S. (1995). Sir Neville Mott: 65 Years in Physics. World Scientific. pp. 153–179. ISBN 978-9810222529.

earlyradiohistory.us

White, Thomas H. (2003). "Section 14 – Expanded Audio and Vacuum Tube Development (1917–1924)". United States Early Radio History. earlyradiohistory.us. Retrieved September 23, 2012.

espacenet.com

worldwide.espacenet.com

German patent 178871 Karl Ferdinand Braun, Wellenempfindliche Kontaktstel, filed: 18 February 1906, granted: 22 October 1906

handle.net

hdl.handle.net

Douglas, Alan (April 1981). "The Crystal Detector". IEEE Spectrum. 18 (4): 64–69. doi:10.1109/MSPEC.1981.6369482. hdl:10366/158938. ISSN 0018-9235. S2CID 44288637. archived: part1, part2, part3, part4

harvard.edu

ui.adsabs.harvard.edu

Braun, F. (1874), "Ueber die Stromleitung durch Schwefelmetalle" [On current conduction through metal sulfides], Annalen der Physik und Chemie (in German), 153 (4): 556–563, Bibcode:1875AnP...229..556B, doi:10.1002/andp.18752291207
Pierce, George W. (July 1907). "Crystal rectifiers for electric currents and electric oscillations, Part 1: Carborundum". Physical Review. 25 (1): 31–60. Bibcode:1907PhRvI..25...31P. doi:10.1103/physrevseriesi.25.31. Retrieved 25 July 2018.
Emerson, D. T. (December 1997). "The work of Jagadish Chandra Bose: 100 years of mm-wave research". IEEE Transactions on Microwave Theory and Techniques. 45 (12): 2267–2273. Bibcode:1997ITMTT..45.2267E. doi:10.1109/22.643830. Retrieved 29 July 2018. also reprinted on IndianDefense Archived 2018-08-09 at the Wayback Machine
Bose, Jagadish Chandra (January 1899). "On electric touch and the molecular changes produced in matter by electric waves". Proceedings of the Royal Society of London. 66 (424–433): 452–474. Bibcode:1899RSPS...66..452C. doi:10.1098/rspl.1899.0124. S2CID 121203904.
Zheludev, Nikolay (April 2007). "The life and times of the LED – a 100-year history" (PDF). Nature Photonics. 1 (4): 189–192. Bibcode:2007NaPho...1..189Z. doi:10.1038/nphoton.2007.34. Archived from the original (PDF) on 2017-03-31. Retrieved 2007-04-11.
Mott, Neville F. (1 May 1939). "The theory of crystal rectifiers". Proceedings of the Royal Society of London, Series A. 171 (944): 27–38. Bibcode:1939RSPSA.171...27M. doi:10.1098/rspa.1939.0051. JSTOR 97313. Retrieved 3 August 2018. reprinted in Alexandrov, A. S. (1995). Sir Neville Mott: 65 Years in Physics. World Scientific. pp. 153–179. ISBN 978-9810222529.

hpfriedrichs.com

Gabel, Victor (October 1, 1924). "The Crystal as a Generator and Amplifier" (PDF). The Wireless World and Radio Review. 15: 2–5. Archived (PDF) from the original on October 23, 2014. Retrieved March 20, 2014.

indiandefence.com

Emerson, D. T. (December 1997). "The work of Jagadish Chandra Bose: 100 years of mm-wave research". IEEE Transactions on Microwave Theory and Techniques. 45 (12): 2267–2273. Bibcode:1997ITMTT..45.2267E. doi:10.1109/22.643830. Retrieved 29 July 2018. also reprinted on IndianDefense Archived 2018-08-09 at the Wayback Machine

jstor.org

Mott, Neville F. (1 May 1939). "The theory of crystal rectifiers". Proceedings of the Royal Society of London, Series A. 171 (944): 27–38. Bibcode:1939RSPSA.171...27M. doi:10.1098/rspa.1939.0051. JSTOR 97313. Retrieved 3 August 2018. reprinted in Alexandrov, A. S. (1995). Sir Neville Mott: 65 Years in Physics. World Scientific. pp. 153–179. ISBN 978-9810222529.

nrao.edu

cv.nrao.edu

Emerson, D. T. (December 1997). "The work of Jagadish Chandra Bose: 100 years of mm-wave research". IEEE Transactions on Microwave Theory and Techniques. 45 (12): 2267–2273. Bibcode:1997ITMTT..45.2267E. doi:10.1109/22.643830. Retrieved 29 July 2018. also reprinted on IndianDefense Archived 2018-08-09 at the Wayback Machine

patents.google.com

U.S. patent 1,104,073 Greenleaf Whittier Pickard, Detector for Wireless Telegraphy and Telephony, filed: 21 June 1911, granted: 21 July 1914
U.S. patent 755,840 Jagadis Chunder Bose, Detector for Electrical Disturbances, filed: 30 September 1901, granted 29 March 1904
U.S. patent 836,531 Greenleaf Whittier Pickard, Means for Receiving Intelligence Communicated by Electric Waves, filed: 30 August 1906, granted: 20 November 1906
U.S. patent 837,616 Henry H. C. Dunwoody, Wireless Telegraph System, filed: 23 March 1906, granted: 4 December 1906
U.S. patent 912,726 Greenleaf Whittier Pickard, Oscillation receiver, filed: 15 September 1908, granted: 16 February 1909

rileyjshaw.com

"The cat’s-whisker detector is a primitive point-contact diode. A point-contact junction is the simplest implementation of a Schottky diode, which is a majority-carrier device formed by a metal-semiconductor junction." Shaw, Riley (April 2015). "The cat's-whisker detector". Riley Shaw's personal blog. Retrieved 1 May 2018.

royalsocietypublishing.org

rspa.royalsocietypublishing.org

Mott, Neville F. (1 May 1939). "The theory of crystal rectifiers". Proceedings of the Royal Society of London, Series A. 171 (944): 27–38. Bibcode:1939RSPSA.171...27M. doi:10.1098/rspa.1939.0051. JSTOR 97313. Retrieved 3 August 2018. reprinted in Alexandrov, A. S. (1995). Sir Neville Mott: 65 Years in Physics. World Scientific. pp. 153–179. ISBN 978-9810222529.

semanticscholar.org

api.semanticscholar.org

Douglas, Alan (April 1981). "The Crystal Detector". IEEE Spectrum. 18 (4): 64–69. doi:10.1109/MSPEC.1981.6369482. hdl:10366/158938. ISSN 0018-9235. S2CID 44288637. archived: part1, part2, part3, part4
"...crystal detectors have been used [in receivers] in greater numbers than any other [type of detector] since about 1907." Marriott, Robert H. (September 17, 1915). "United States Radio Development". Proceedings of the Institute of Radio Engineers. 5 (3): 184. doi:10.1109/jrproc.1917.217311. S2CID 51644366. Retrieved 2010-01-19.
Bose, Jagadish Chandra (January 1899). "On electric touch and the molecular changes produced in matter by electric waves". Proceedings of the Royal Society of London. 66 (424–433): 452–474. Bibcode:1899RSPS...66..452C. doi:10.1098/rspl.1899.0124. S2CID 121203904.

semiconductormuseum.com

https://www.semiconductormuseum.com/MuseumLibrary/HistoryOfCrystalDiodesVolume1.pdf

soton.ac.uk

orc.soton.ac.uk

Zheludev, Nikolay (April 2007). "The life and times of the LED – a 100-year history" (PDF). Nature Photonics. 1 (4): 189–192. Bibcode:2007NaPho...1..189Z. doi:10.1038/nphoton.2007.34. Archived from the original (PDF) on 2017-03-31. Retrieved 2007-04-11.

stanford.edu

www-smirc.stanford.edu

Lee, Thomas H. "A Nonlinear History of Radio". The design of CMOS radio frequency integrated circuits (PDF). p. 5. OCLC 247748263. Archived (PDF) from the original on 6 October 2022. Retrieved 8 August 2023. In any event, we can see how the modern symbol for the diode evolved from a depiction of this physical arrangement, with the arrow representing the catwhisker point contact, as seen in the figure.

web.archive.org

Lee, Thomas H. "A Nonlinear History of Radio". The design of CMOS radio frequency integrated circuits (PDF). p. 5. OCLC 247748263. Archived (PDF) from the original on 6 October 2022. Retrieved 8 August 2023. In any event, we can see how the modern symbol for the diode evolved from a depiction of this physical arrangement, with the arrow representing the catwhisker point contact, as seen in the figure.
Emerson, D. T. (December 1997). "The work of Jagadish Chandra Bose: 100 years of mm-wave research". IEEE Transactions on Microwave Theory and Techniques. 45 (12): 2267–2273. Bibcode:1997ITMTT..45.2267E. doi:10.1109/22.643830. Retrieved 29 July 2018. also reprinted on IndianDefense Archived 2018-08-09 at the Wayback Machine
Grebennikov, Andrei (2011). RF and Microwave Transmitter Design. John Wiley & Sons. p. 4. ISBN 978-0470520994. Archived from the original on 2016-09-17.
Gabel, Victor (October 1, 1924). "The Crystal as a Generator and Amplifier" (PDF). The Wireless World and Radio Review. 15: 2–5. Archived (PDF) from the original on October 23, 2014. Retrieved March 20, 2014.
Ben-Menahem, Ari (2009). Historical Encyclopedia of Natural and Mathematical Sciences, Vol. 1. Springer. p. 3588. ISBN 978-3540688310. Archived from the original on 2017-11-23.
Zheludev, Nikolay (April 2007). "The life and times of the LED – a 100-year history" (PDF). Nature Photonics. 1 (4): 189–192. Bibcode:2007NaPho...1..189Z. doi:10.1038/nphoton.2007.34. Archived from the original (PDF) on 2017-03-31. Retrieved 2007-04-11.

worldcat.org

search.worldcat.org

Douglas, Alan (April 1981). "The Crystal Detector". IEEE Spectrum. 18 (4): 64–69. doi:10.1109/MSPEC.1981.6369482. hdl:10366/158938. ISSN 0018-9235. S2CID 44288637. archived: part1, part2, part3, part4
Lee, Thomas H. "A Nonlinear History of Radio". The design of CMOS radio frequency integrated circuits (PDF). p. 5. OCLC 247748263. Archived (PDF) from the original on 6 October 2022. Retrieved 8 August 2023. In any event, we can see how the modern symbol for the diode evolved from a depiction of this physical arrangement, with the arrow representing the catwhisker point contact, as seen in the figure.
Lukasiak, Lidia; Jakubowski, Andrzej (January 2010). "History of Semiconductors" (PDF). Journal of Telecommunications and Information Technology. ISSN 1509-4553. Retrieved 2 August 2018.