What Is A Modem?

The modem word, which is a combination of the words modulator and demodulator, is basically a foreign abbreviation, as you can see. The modem is a device that allows the computers we use at home and office to connect to a public network and that allows the computer to access other computers.

  • Modulation: the conversion of the numeric data reaching the modem to analog signals compatible with the telephone line.
  • Demodulation: the process of converting this data from analog signals to digital data as a result of the modem receiving data.

Modem Types

The limitation and diversification of modems is done by the amount of data that the modem sends at a time. This amount is measured by the unit called Bit. There are two types of modems based on this limitation and diversification:

1- Internal Modems

One of the active duty modems. It can be installed directly into the main bus of your computers. That’s exactly why he’s active. The software is controlled. It can also operate via COM port without using the port of the device. Since the fixed series is not used, it needs to be adjusted by means of the jumpers on it.


2 – External (External) Modems
They are box-shaped modems that connect directly to the computer via cables. There are various cable entries on these box-shaped modems. With these cable inputs, the modem has its own power supply input.

There are lights on these modems to give information about the usage status. When a problem is experienced instantly through these lights, it is immediately revealed why this problem is caused. Therefore, you need to know the meaning of these lights.

What Does The Modem Lights Mean?

HS: means high speed. The light illuminates when the modem is connected faster than 2400bps.
AA: means automatic answer. When left in auto answer, the light illuminates.
CD: means the connection was established. The light illuminates when the connection to the opposite modem is established.
Oh: even means. The light illuminates when the modem receives the telephone line.
SD: means sending data. The light illuminates when the modem starts sending data.
Rd: means that you are receiving data. The light illuminates when the modem begins to receive data.
TR: modem ready means. The light illuminates when you switch to the terminal screen in the modem program.
Mr: means the modem is turned on. The light illuminates when the modem is turned on.

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