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Quick links
Modem ABCs
ATI Command Explanation
X2, KFlex, V.90 Information
Hayes AT String information
Troubleshooting
Modem definitions
MODEM ABCs
Short for MODulator / DEModulator, which describes the method used to convert
digital data used by computers into analog signals used by the phones and then back into
digital data once received by the other computer.
The above pictures help represent a digital signal and an analog signal. All computer
data is stored and transmitted within the computer in digital format 1s and 0s. In order
for this data to be transmitted over analog phone lines, the data must be transmitted into
an analog signal which is the noise you hear when connecting to another computer. Once the
other computer receives this signal, it will then translate the signal back into its
original digital format.
Typical modems are referred to as an asynchronous device, meaning that the
device transmits data in an intermittent stream of small packets. Once received, the
receiving system then takes the data in the packets and reassembles it into a form the
computer can use.
Stop
1 bit |
Data
8 bits |
Start
1 bit |
Stop
1 bit |
Data
8 bits |
Start
1 bit |
Packet
10 bits |
Packet
10 bits |
The above chart represents how an asynchronous transmission would be transmitted over a
phone line. In asynchronous communication, 1 byte (8 bits) is transferred within 1 packet,
which is equivalent to one character. However, for the computer to receive this information,
each packet must contain a Start and a Stop bit; therefore, the complete packet would be 10
bits. An example of what the above chart would transmit is the word
HI
which is equivalent to 2 bytes (16 bits).
There are two types of modems used in all computers.
Internal: Modem which would be plugged into a slot located within or
on the computer.
External: Modem which is located within a box and is hooked up
externally to the computer, generally VIA the Serial Ports.
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ATI
Command explanation
ATI commands are to get various
information on your modem. To get any of the below information, you will need to type
the ATI commands from a communications software or if you have Windows
95 or Windows 98 by going into start / settings / Control Panel / modems / clicking on the tab that says diagnostics / and highlighting the port
that the modem is listed on and clicking on the more info button.
ATI0 = Return Product Code
ATI1 = Return memory (ROM) checksum
ATI2 = Run memory (RAM) test
ATI3 = Return call duration/real time
ATI4 = Return current modem settings
ATI5 = Return NVRAM settings
ATI6 = Return link diagnostics
ATI7 = Return product configuration |
MODEM
AT Strings
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