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Speaker 1: Jack Threads is the online shopping destination for dudes. Everything

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Speaker 1: on the side is up to off, all styles are curated,

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Speaker 1: so buyer's remorse just doesn't happen. What's more is if

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Speaker 1: you were brain stuff, you can skip the membership wait

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Speaker 1: list and get instant access at jack threads dot com

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Speaker 1: slash stuff. Welcome to Brainstuff from house stuff works dot

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Speaker 1: com where smart Happens. Hi, I'm Marston Brain with today's question.

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Speaker 1: Why is a cell phone called a cell phone? One

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Speaker 1: of the most interesting things about a cell phone is

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Speaker 1: that it's really a radio. It's really an advanced walkie talkie,

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Speaker 1: if you want to think about it. Before cell phones,

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Speaker 1: people who needed mobile communications installed radio telephones in their car.

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Speaker 1: In the radio telephone system, there was one big central

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Speaker 1: antenna per city and maybe a handful of channels that

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Speaker 1: were available on that antenna. You had to put this big,

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Speaker 1: high powered radio in your car. And when I say big,

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Speaker 1: I mean like it filled half your trunk. And it

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Speaker 1: had to be big because if you were twenty miles

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Speaker 1: away from that central tower, you had to transmit at

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Speaker 1: thirty watts or something. You had a radio station in

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Speaker 1: your car to use this system. The idea of a

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Speaker 1: cell phone changed all that completely. The cellular phone system

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Speaker 1: divides this city into a bunch of small cells. This

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Speaker 1: allows extensive frequency reuse across the city, so that millions

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Speaker 1: of people can use cell phones simultaneously. Here's how it works.

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Speaker 1: The carrier chops up an area such as the city,

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Speaker 1: into these cells. Each cell is typically sized at about

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Speaker 1: ten square miles perhaps three miles by three miles. Cells

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Speaker 1: are normally thought of as hexagons on a big hexagonal grid.

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Speaker 1: Each cell has a base station that consists of a

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Speaker 1: tower and a small building containing the radio equipment. Cell

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Speaker 1: phones have low power transmitters in m and the base

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Speaker 1: station is also transmitting at low power. Low power transmitters

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Speaker 1: have two advantages. First, the power consumption of the cell phone,

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Speaker 1: which is normally battery operated, is relatively low. Low power

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Speaker 1: means small batteries, and this is what has made handheld

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Speaker 1: cellular phones possible. Second, the transmissions of the base station

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Speaker 1: and the phones within its cell do not make it

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Speaker 1: very far outside that cell. Therefore, the same frequencies can

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Speaker 1: be reused extensively across the city. The cellular approach requires

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Speaker 1: a large number of base stations in a city of

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Speaker 1: any size. A typical large city can have hundreds of towers,

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Speaker 1: but because so many people are using cell phones, costs

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Speaker 1: remain fairly low per user. Each carrier in each city

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Speaker 1: also runs one central office called the Mobile Telephone Swishing

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Speaker 1: Office or MTSO. This office handles all the phone connections

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Speaker 1: to the normal land base phone system and controls all

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Speaker 1: the base stations in the region. As you move towards

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Speaker 1: the edge of your cell, so you're in a car

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Speaker 1: and you're driving away from the tower for your cell,

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Speaker 1: your cells base station will note that your signal strength

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Speaker 1: is diminishing. Meanwhile, the base station in the cell you're

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Speaker 1: moving toward, which is listening and measuring the signal strength

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Speaker 1: on all frequencies, not just its own one seventh of

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Speaker 1: the frequency spread, we'll be able to see that your

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Speaker 1: phone signal strength is increasing. The two base stations coordinate

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Speaker 1: themselves through the mt s O, and at some point

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Speaker 1: your phone gets a signal on a control channel telling

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Speaker 1: it to change frequencies. This handoff switches your phone to

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Speaker 1: the new cell, and you don't even know it's happening.

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Speaker 1: In most cases, as you're driving down Interstate Highway, for example,

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Speaker 1: your phone might switch towers every five minutes, and that's

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Speaker 1: completely invisible to someone who's making an hour long call.

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Speaker 1: For more on this and thousands of other topics, is

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Speaker 1: it how staff works dot com. Jack Threads is the

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Speaker 1: online shopping destination for dudes. Everything on the side is

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Speaker 1: up to eight off, All styles are curated, so buyer's

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Speaker 1: remorse just doesn't happen. What's more is, if your brain stuff,

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Speaker 1: you can skip the membership wait list and get instant

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Speaker 1: access at jack threads dot com. Slash stuff