What Do the Second 3 Digits of a Phone Number Mean?
Breaking Down the U.S. Phone Number Structure
Most U.S. phone numbers follow the same pattern: (XXX) XXX-XXXX. But have you ever stopped and wondered what those middle three digits actually mean?
Area Code vs. Central Office Code vs. Line Number
The first three digits are the area code — pretty straightforward. They represent a geographical region, like 212 for Manhattan or 310 for parts of Los Angeles.
The last four digits? That’s your line number — kind of like your personal ID in that exchange.
But the middle three digits? Ah, those are called the central office code, and they hold more meaning than most people think.
What Is the Central Office Code?
The central office code (a.k.a. the exchange code or prefix) is that second set of three digits. It identifies a specific telephone exchange within the area code.
What is a telephone exchange?
Back in the old days (like, rotary phone days), each area had a central office. These were literal buildings filled with switchboards and operators. Your phone line was wired to one of them.
The exchange code was used to route calls to the right switchboard. These days it's all digital, but the logic behind it is still the same: it determines where your call goes within the area.
Example: In (212) 555-1234, “555” is the central office code. It tells the network, “Yo, this is in the 555 exchange within 212.”
Are Central Office Codes Still Location-Based?
Well... kinda. But not always. That’s where things get messy (and a bit techy).
Originally? Yes.
Once upon a time, every central office code corresponded to a fixed place. So (213) 468-XXXX might all be downtown L.A., while (213) 987-XXXX might be out in Echo Park.
Now? Not necessarily.
Since number portability came into play, and with VoIP services, mobile phones, and virtual numbers, central office codes don’t always tie neatly to a location anymore. You can have a “New York” number and be living it up in rural Montana.
So yeah, the exchange still kind of hints at a region, but it’s not a guarantee anymore. It’s more of a historical artifact — like your old Myspace profile.
Weird Facts About Central Office Codes
Not all numbers are real
“555” used to be reserved for fake numbers in movies and TV. You know, so poor souls wouldn’t get thousands of prank calls after a rom-com hit theaters.
Some combos are off-limits
The FCC avoids certain number combos to prevent confusion — like those starting with “0” or “1” in the central office section. (They look too much like operator numbers or long-distance codes.)
So... Should You Care?
If you’re a telecom nerd or just curious — sure. But most people never need to think about it. The central office code is baked into your number when it’s assigned, and unless you’re moving carriers or setting up a vanity number, you won’t interact with it.
That said, it can sometimes give you a little hint about where someone’s number came from... emphasis on sometimes.
Bottom line: the second 3 digits in your phone number — the central office code — were originally designed to route your call within your area. While today it’s less rigidly tied to geography, it still plays a key role in how your call gets from Point A to Point B. Hidden tech magic in just three little digits. Neat, huh?
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Is 172 cm good for a man?
Yes it is. Average height of male in India is 166.3 cm (i.e. 5 ft 5.5 inches) while for female it is 152.6 cm (i.e. 5 ft) approximately. So, as far as your question is concerned, aforesaid height is above average in both cases.
Is 165 cm normal for a 15 year old?
The predicted height for a female, based on your parents heights, is 155 to 165cm. Most 15 year old girls are nearly done growing. I was too. It's a very normal height for a girl.
Is 160 cm too tall for a 12 year old?
How Tall Should a 12 Year Old Be? We can only speak to national average heights here in North America, whereby, a 12 year old girl would be between 137 cm to 162 cm tall (4-1/2 to 5-1/3 feet). A 12 year old boy should be between 137 cm to 160 cm tall (4-1/2 to 5-1/4 feet).
How tall is a average 15 year old?
Average Height to Weight for Teenage Boys - 13 to 20 Years
| Male Teens: 13 - 20 Years) | ||
|---|---|---|
| 14 Years | 112.0 lb. (50.8 kg) | 64.5" (163.8 cm) |
| 15 Years | 123.5 lb. (56.02 kg) | 67.0" (170.1 cm) |
| 16 Years | 134.0 lb. (60.78 kg) | 68.3" (173.4 cm) |
| 17 Years | 142.0 lb. (64.41 kg) | 69.0" (175.2 cm) |
How to get taller at 18?
Staying physically active is even more essential from childhood to grow and improve overall health. But taking it up even in adulthood can help you add a few inches to your height. Strength-building exercises, yoga, jumping rope, and biking all can help to increase your flexibility and grow a few inches taller.
Is 5.7 a good height for a 15 year old boy?
Generally speaking, the average height for 15 year olds girls is 62.9 inches (or 159.7 cm). On the other hand, teen boys at the age of 15 have a much higher average height, which is 67.0 inches (or 170.1 cm).
Can you grow between 16 and 18?
Most girls stop growing taller by age 14 or 15. However, after their early teenage growth spurt, boys continue gaining height at a gradual pace until around 18. Note that some kids will stop growing earlier and others may keep growing a year or two more.
Can you grow 1 cm after 17?
Even with a healthy diet, most people's height won't increase after age 18 to 20. The graph below shows the rate of growth from birth to age 20. As you can see, the growth lines fall to zero between ages 18 and 20 ( 7 , 8 ). The reason why your height stops increasing is your bones, specifically your growth plates.