What is caller ID?
To put it simply caller ID allows a person to see the phone number of the person calling and most of the time also the name. The number and sometimes name will be displayed on the phone, computer, or caller ID box, along with the date and time the person called. Most telephones and caller ID boxes will save a list of up to 99 numbers so you can check them later. This can be very useful if you are not willing to take certain calls, you can tell who is calling before hand.

How do I use caller ID?
In order to use caller ID you need a few things. First off a phone that accepts caller ID, or a caller ID box, or you can have caller ID software on your computer. However to use caller ID on your computer you need a modem that allows it. Make sure to check first. Second you need to have the service from your telephone company. Just a quick call can usually solve this. Just one little other thing that you might need is an additional phone cord for the caller ID box. You don't need an additional one for your phone because it is built in. And most caller ID boxes will come with an additional cord.

How much is it going to cost?
The monthly charges can range from phone company to phone company. In Halstad, MN it costs $2.50/mo. for caller ID number, and $3.50/mo. for caller ID name and number. From Qwest, the average cost is around $6.95/mo. You can get a caller ID phone for almost the same price as a regular phone, maybe up to $10.00 more. You can usually get a caller ID box for about $10.00 to $20.00 depending on the features you choose to get and the brand name. A lot of phone companies will in fact give you the caller ID box just for signing up.

How does caller ID work?
The phone company uses what is called frequency shift keying or FSK to transmit the callers data just like a 1,200 baud modem would. They send the data using ASCII format to the caller ID box, or phone. All of the data is sent in the first or second ring so you can get it right away. Frequency shift keying works by sending a frequency down the line to represent a 1 or a 0. Just like in binary code. Like 1,200 hertz to represent a binary 1 and 2,200 hertz to represent a binary 0. A modem changes frequencies depending on whether it wants to send a 1 or a 0. How quickly it changes frequencies determines the speed, or baud rate, of the modem. The caller ID box or phone has a modem in it to decode the data and display it on the screen. It also contain a little circuit to detect a ring and a very small processor. If you could here the just after the initial ring you would hear a small beep containing the data. If you decoded the beep you would get all the information sent to the caller ID box. To be more specific it would contain a series of alternating 1s and 0s to help the caller ID box get the timing down, a series of 180 1s, a byte representing the type of message, a byte representing the length of the message, Month, day, hour and minute, each represented with a pair of bytes, the 10 digit phone number in 10 bytes, and a checksum byte

How come people's numbers show up unavailable?
When people call you they have the option of leaving out their number by dialing *67 before they call. You too can dial *67 before you call and have your information blocked if you would like. Or if you are living in the UK you can dial 141 before your call. Another reason for this is because phone companies will hold back the name and number of a unlisted numbers. Sometimes you will also see unavailable if the system a person is calling from doesn't support caller ID or is out of range. You can fight back against unavailable numbers because of Anonymous Call Rejection (ACR or block blocking). This service should be available for free from your telephone company. A lot of the time a unavailable number is a telemarketer this will help stop the unwanted calls.

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