▷ Modem: what it is, how it works and a bit of history

The modem has been used for many years to establish the Internet connections of our computer equipment. Currently it is almost necessary to be connected to the Internet, the network of networks, where we can find almost anything we are looking for. One of the key devices for the history of the Internet is the modem, and today we will see what it is about, how it works and what were the first steps of these devices.

Index of contents

What is the modem

In the early days of the Internet, one of the most widely used transmission media for data connection was the Basic Telephone Network or (RTB), which had wide coverage and relatively low cost. In fact, the cabling network itself was used for voice transmission. The problem with using this network is that the signals were analog (voice) and not digital (data).

Precisely from this need to convert analog signals to digital, the modem or MOdulator / DEModulator was born. So a modem is a device capable of converting digital signals to analog, a process called " modulation ", and is also capable of converting analog signals to digital, whose process is called " demodulation ".

What a modem basically does is allow communication between our computer and the Internet through the telephone network or the so-called cable modem, which uses the cable television network, something that will sound old to us.

How does a modem work then?

The modem is responsible for receiving information from the Internet service provider (ISP) through the phone or a coaxial cable in the case of a cable modem. Upon receiving this signal, the modem converts it to digital and sends it to the device that is connected to it. In a modem, only one device can be connected at a time, since it does not have multiple routing capacity as current routers are capable.

To understand this process of "translation" of an analog signal into digital and vice versa, we will have to understand a little about the waves and their characteristics.

When transmitting information, we must differentiate two types of signals, the carrier signal and the modulating signal. These signals are, in short, sine waves that are responsible for carrying information from one point to another. These waves have three important parameters, the frequency (Hz), the amplitude (Volts) and the phase (degrees). First of all, the information is processed to introduce it into a modulating signal, this action is what the modem does, prepares and modulates the information. Next, a carrier signal is emitted that will be modified in some way by the modulator signal, let's say it gives it a unique characteristic to differentiate it from other signals that exist in the transmission medium. In this way we can transmit the modulated data, so that they can be demodulated at the other end of the connection. The demodulation process will consist of extracting the original modulating signal from the carrier signal, and thus converting the signal into useful data for the equipment.

Modulation types

But this is not all. We have said that the modulating signal modifies the carrier, but how? Well, there are three ways to modify a carrier, and as you may have guessed, it will be modifying any of the three characteristics of the frequency.

• Amplitude modulation: in this modulation the amplitude pattern of the transmitted wave is modified. It is also called ASK or AM (amplitude modulated), this will all sound familiar to us from the radio, the process is the same. Frequency modulation: in this case we would be modifying the frequency of the transmitted wave, modifying its period at different frequencies. Also called FSK or FM (frequency modulated). Modulation by phase: in the last case we will be modifying the phase of the transmitted wave. Also called PSK or PM.

A little history of the modem

With the modem, the Internet age begins, if Graham Bell raised his head, he would hallucinate with what has been achieved thanks to his inventions. Well, it all started back in 1958, when the first modem was invented. It seems very far away, but most of our parents would be born at that time. At least those of us from the 80-90s. In this modem, it was possible to transmit binary data on a telephone line.

Then comes the first point-to-point data network, called ARPANET, whose creator and key figure was Larry Roberts who didn't leave last year. This network was implemented for the United States Department of Defense, and it would be in 1990 when it stopped being called like that due to the great advances and the extension that it reached.

And then came the modem

Then the World Wide Web (WWW) appeared, where we were already talking about millions of interconnected computers. It was in this decade where the telephone network began to be used as a means of connecting to the Internet, for this, a normally nice man came with a device called a modem and connected it directly to the telephone rosette, using an RJ11 and a two twisted pairs. Of course our mother was pissed off and we with her, since talking on the phone and connecting to the Internet simultaneously was only possible in the movies. And is that because the same signal was used for voice and data, speaking and browsing was impossible to do at the same time.

As if that were not enough, this modem was able to provide us with a bandwidth of no less than 56 Kbps in its latest versions, after carrying out a connection process full of dialing sounds and various chirps. You can imagine the "millennia" how sophisticated the web pages of the time were, finding an image was the novamás.

The connections were gaining in benefits and new technologies such as ISDN and later ADSL and cablemodem appeared. With ADSL we used (and use) the telephone network itself to connect to the Internet, and with the cablemodem we used the cable television connection. These new technologies based on digital connections, already abandoned the modem to focus on so-called network cards and routers. From here on, fiber optic and wireless connections began to appear, until today.

The use of the modem today

Before we have spoken for example of the ISDN and ADSL network, and we must bear in mind that this network is no longer analog. Although it is true that we still call the device that we connect between our PC and ADSL modem, it is not correct, since this function is what makes a network card, or in your case a router.

The modem is only used for analog connections, and we must always keep this in mind. A digital Internet connection does not require modulation and demodulation, since communication is direct through a network interface or network card.

The fact of calling a phone modem when we configure it as a Wi-Fi modem, for example, means that we are giving the possibility of other devices connecting to it to access the Internet through it. In this case, the mobile would act as a means of connection between the Internet and a laptop, translating the signal so that they understand each other, but it will always be a digital and not an analog signal. What's more, a real modem can only connect with one device and not with several at the same time.

We also find a very common use of the modem for Faxes, which is one of the few means in which this type of device is still functional. As we know, a fax allows us to transmit a text message by analog signal, where a paper printing system is responsible for generating it.

In summary, don't confuse a modem with a network card or a router, because they are different elements.

Modem types and connections

Let's now look at the types of modem that have existed over time:

• Internal Modem: These modems consist of an expansion card that connects to the motherboard of our computer. It will consist of a PCB with the components of a modem and an interface based on the latest ISA, AMR or PCI bus.

• External Modem: in this case we will have a device that connects to the computer through a serial port, for example, USB. They are generally used to perform the answering machine or fax functions.

• External PCMIA modem: they are also external modems, but smaller than the previous ones and connected by PCMCIA to portable computers.

• HSP software modem: also called winmodems, which are internal modems whose modulator / demodulator function is performed by the computer's own processor. For this we must use computer software that generates the corresponding instructions typical of a modem.

Standards used by modems

If we talk about modem, we must also talk about the regulations that are used for its operation. This standard is often referred to as the Telecommunication Standardization Sector V-Series or CCITT, currently called ITU-T. Let's see the most relevant:

Rule	Speed
V.22	1, 200 / 600 bit (old laptops)
V.22 bis	2, 400 bit (basic telephone network)
V.29	9, 600 bit (FAX)
V.32 / V.32bis	9, 600 / 14, 400 bit (phone lines)
V.34	28, 800 bit (two-wire analog lines)
V. 34bis	33, 600 bit (minimum to access the Internet)
V.92bis	56 Kbit / s the most current (Internet access from RTC)

Although there are more variants, these are the ones that have been considered the most important and most relevant in the history of the modem.

Conclusion about the modem and its use

We should now know more precisely what the modem consists of and what it has been used for in our recent past. It has been a very important device and it has marked, in some way, the beginning of networks with Internet access.

Surely many of you have not even met him, or you will have directly entered the world of the internet directly with ADSL or at most with the ISDN network.

We hope you found this information about the modem and its use useful. Now we leave you with a few articles that could be interesting to learn about other aspects of the world of networks.

The question is obligatory. Have you ever used a modem? Write us to tell us if you have ever had contact with them.