The first (number system) digit in the 12-digit UPC Version A (Universal Product Code for North America) barcode is 3 for drugs, beauty aid and health products, (followed by 5-digit manufacturing code, 5-digit product code and 1 check digit at the right end).
The number of hands on a regular mechanical clock or watch, showing hours, minutes and seconds.
The number of primary colors of paper printing inks (for books, magazines…) or dyes: cyan, magenta and yellow, (together with black). Mixing these 3 primary colors gives black. They are 3 secondary colors of light.
The number of secondary colors by mixing primary colors of paper printing inks (for books, magazines…) or dyes: red (magenta and yellow with equal amount), blue (magenta and cyan) and green (yellow and cyan). They are 3 primary colors of light.
The number of primary colors of light (such as for TV screen): red, blue and green. They are 3 secondary colors of pigments. Mixing these 3 primary colors of lights gives white.
The number of secondary colors of light (such as for TV screen): yellow (mixing red and green with equal amount), cyan (blue and green) and magenta (red and blue). They are 3 primary colors of pigments.
The number of letters in the name codes for U.S. radio stations, assigned by the Radio Act in 1912. Other: 4.
Rule of thumb: Twice as much power or intensity of sound is measured by 3 decibels (or exactly 10×log102) decibels higher.
The name “3M” stands for “Minnesota Mining and Manufacturing Company”, founded in Two Harbors, Minnesota in 1902.
The popular Alkaline-Manganese battery voltages for household electronic devices: 1.5V – 3V – 4.5V – 6V – 9V, available in popular sizes: AAA, AA, C, D, G and N. The Carbon-Zinc batteries have additional values: 12V – 22.5V – 45V and 90V. Other values: PP3 – 1.2V – 3.6V – 4.8V – 8.4V for Ni-Cad rechargeables.
The powers of commercial incandescent light bulbs: 300W, 100W, 75W, 60W, 40W, 30W, 15W, 7.5W and 3W.
Nuclear accident at Three Mile Island (near Harrisburg, Pennsylvania) occurred in 1979. (The island may be actually only 2.5-mile long).
The “number system” code of an EAN-13 barcode for the U.S. and Canada’s products: 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 10, 11, 12 and 13.
Frequency Ranges
|
Range |
Names |
Uses |
|
3 Hz – 300 Hz |
Extremely Low Frequency (ELF) |
Telegraph |
|
300 Hz – 3 KHz |
Voice Frequency (VF) |
Telephone Circuitry |
|
3 KHz – 30 KHz |
Very Low Frequency (VLF) |
High Fidelity |
|
30 KHz- 300 KHz |
Low Frequency (LF) |
Maritime Mobile |
|
300 KHz – 3 MHz |
Medium Frequency (MF) |
Navigational Radio, Land-maritime Mobile |
|
3 MHz – 30 MHz |
High Frequency (HF) |
Maritime, Aeronautical, Amateur Radio |
|
30 MHz – 300 MHz |
Very High Frequency (VHF) |
Maritime, Meteorological Communication, Television |
|
300MHz – 3 GHz |
Ultra High Frequency (UHF) |
Television, Military, Low Range Radar |
|
3 GHz – 30 GHz |
Super High Frequency (SHF) |
Space, Satellite, Microwave |
|
30 GHz – 300 GHz |
Extremely High Frequency (EHF) |
Radio Astronomy |
3.6
The voltage of a Ni-Cad rechargeable battery of type AA, AAA, C, D and N is usually 1.2V (less than 1.5V of non-rechargeable batteries). Other values: PP3 – 1.2V – 3.6V – 4.8V – 8.4V.
