DECIMAL CLASSIFICATION 
621.3 Electric engineering 
oor Statistics; 002 Quantities and cost; 003 Contracts and specifications; 
004 Designs and drawings; oos Executiv; 006 Working and maintenance; 
007 Laws and regulations; 008 Patents; 009 Reports 
May also be subdivided for form with o like 620.1—.9 
SUMMARY 
621.31-7 Hevy current engineering 
31 Generation of electricity 
311 General 
312 Central stations 
313 Dynamoelectric machinery 
314 Stationary induction apparatus 
315 Electrostatic apparatus 
316 Accessories and parts 
2ar7 Control and central station wiring 
z Transmission - 
Electric lighting 
Electric traction 
Voltaic cells and batteries 
5X 
312 
. 
37 Rlectric measurements and testing 
38 Weak current engineering 
382 Telegrafy 
384 Wireless communication 
385 Telefony 
39 Other applications of electricity 
621.31-.37 Hevy cu:rent engineering 
Generation of electricity Dynamoelectric machinery 
Transformers Transmission 
General 
Central stations: metropolitan, rural 
Divided by oor-o09 like 621.3 with the following additions to 006 
006 Working and maintenance 
Operation and running 
Regulation and control 
Testing 
Repairs and renewal 
Administrativ point of view; a specific repair belongs with 
the part repaird 
General central stations 
Combined power, traction, light, etc. stations 
Steam driven 
Gas “ 
Hydraulic 
Composit 
Stations for lighting only 
Divided by source of power like 621.31213 
Stations for tractiononly 
Divided like 621.31213 
Storage battery pressure regulating equipment 
Substations 
Transformer substations 
Converter “ 
Accumulator ® 
.3 
132 
133 
134 
135 
6 
63 
64 
63