I have a mobile phone. No, it isn't a cellular phone. It's a cordless phone and I love it. I can work on the laundry or putter about in the kitchen or even go out and get the mail and still be able to converse on the phone.
But, I admit, that's not what most people think of when you say a mobile phone. So, what is?
A phone has basically two parts. One part connects to the network, or phone company, or central office, or carrier, or whatever term you want to use. Over that part, the information related to how, and to whom, you want to connect to someone else is conveyed. There are a lot of different mechanisms from POTS (Plain Old Telephone System), to ADSL (sometimes the "A" is dropped nowadays), to ISDN, to optical fiber using a version of ATM over SONET. What do all those mean? Not much to most people although it is important to the service provider and makes a difference as to what things you can do over your phone. The main point is that it lets you be called and make calls.
The other part is the control part. Usually that means a keypad but it may be voice activated or have a touch pad. This lets you enter in the information needed to connect to whom you want to connect -- or make use of the services provided (call waiting, Instant Messaging, etc.).
The control part can be all in one unit -- traditional phone or "cell phone". Or, as in the case of my cordless phone, it can be separated from the control base and the information exchanged very locally (usually less than 500 feet).
The point of a mobile phone is mobility. Presently, that means more than 500 feet to most people. What do you need for that?
Basically, you have to extend your "access point". The access point is where you connect to the network. A "landbased" line has a physical line that connects to a jack in the wall (well, there are some other ways -- but that's the way almost all are connected). A "cellular" phone connects via "airwaves" (let's leave out the various frequency bands for the moment) to a transmission tower which is the access point.
And that is what is meant by a mobile phone -- extending the access point. How is that done? Stay tuned for that in the next post.
