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Melvil Decimal System: 621.3840

Wording: Technology > Engineering > Mechanical Engineering and Machinery > Electric engineering > Electronics, Communications. > Radar, Radio. > Not set

Dewmoji: 💡 > 🔩 > 🏭 > ? > ? > ? > ?

0
Information
174,442
ℹī¸
1
Philosophy and Psychology
161,809
💭
2
Religion
423,445
🙏đŸŊ
3
Social Sciences
881,483
đŸ‘Ģ
4
Language
118,029
đŸ’Ŧ
5
Mathematics and Science
274,025
đŸ”Ŧ
6
Technology
639,380
💡
7
Arts and Recreation
651,545
🎨
8
Literature
865,381
📚
9
Biography and History
551,058
đŸ—ŋ
60
General Technology
6,246
💡
61
Medicine
207,724
💉
62
Engineering
102,568
🔩
63
Agriculture & Animal Husbandry
61,853
🌱
64
Home Economics
123,000
🏠
65
Business
99,261
👔
66
Chemical Technology
11,503
🚀
67
Manufacturing
4,874
đŸ“Ļ
68
Handicraft and Occupations
14,129
🔨
69
Building
8,222
👷
620
Engineering
12,105
🔩
621
Mechanical Engineering and Machinery
31,214
🏭
622
Mining Engineering and Mines and Mineral Resources
2,345
đŸ•ŗ
623
Military Engineering and Marine Engineering
10,859
⚓
624
Civil Engineering
5,409
🌉
625
Road and Railroad
3,420
🛤
626
--
29
🤷
627
Hydraulic Engineering
1,059
🌊
628
Sanitary; Municipal
4,548
đŸšŊ
629
Other Branches
31,580
đŸŒŋ
621.0
536
621.1
Steam engineering
377
621.2
Hydraulic machinery
172
621.3
Electric engineering
21,836
621.4
Heat engineering
2,252
621.5
Pneumatic machinery and Compressed air and Refrigeration and refrigerating machinery
274
621.6
Fans (Machinery) and Pumping machinery
99
621.7
Production engineering and Factories and Machine-shop practice
83
621.8
Other mechanical engineering topics
1,780
621.9
Machine-tools
873
621.30
366
621.31
2,858
621.32
266
621.33
22
621.34
77
621.35
23
621.36
1,810
621.37
81
621.38
Electronics, Communications.
13,625
621.39
Computers
1,749
621.380
Light current engineering
214
621.381
Electronics
5,789
621.382
Communications
2,778
621.383
Telegrapy
21
621.384
Radar, Radio.
2,500
621.385
Telephony
257
621.386
Telephone terminal equipment
56
621.387
Telephone transmission equipment
19
621.388
Television
598
621.389
Audio, sound engineering
770
621.3840
87
621.3841
Amateur radio
1,001
621.3842
15
621.3843
4
621.3844
1
621.3845
538
621.3846
4
621.3847621.3848
Radar
229
621.3849
621.38400
2
621.38401
7
621.38402
16
621.38403
4
621.38404
1
621.38405
1
621.38406
1
621.38407
9
621.38408
3
621.38409
43

Works under MDS 621.3840

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Wording

1922 Edition
Modern language
Emoji

"Far Friends"

MDS classes with significant recommendations overlap, excluding ones under the same top-level class.

None

What is MDS?

Melvil stands for "Melvil Decimal System," named after Melvil Dewey, the famous librarian. Melvil Dewey invented his Dewey Decimal System in 1876, and early versions of his system are in the public domain.

More recent editions of his system are in copyright, and the name "Dewey," "Dewey Decimal," "Dewey Decimal Classification" and "DDC" are registered trademarked by OCLC, who publish periodic revisions.

LibraryThing's MDS system is based on the classification work of libraries around the world, whose assignments are not copyrightable. MDS "scheduldes" (the words that describe the numbers) are user-added, and based on public domain editions of the system.

The Melvil Decimal System is NOT the Dewey Decimal System of today. Wordings, which are entered by members, can only come from public domain sources. The base system is the Free Decimal System, a public domain classification created by John Mark Ockerbloom. Where useful or necessary, wording comes from the 1922 edition of the Dewey Decimal System. Language and concepts may be changed to fit modern tastes, or to better describe books cataloged. Wordings may not come from in-copyright sources.

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