Hardware: Dial-up Modems

Equipment:

As shown earlier, the first commercial modem made by Bell used a
receiver that a standard phone handheld receiver/sender would
physically lay on top in order to send the analog tones needed to
work a dial-up modem at that point in time. Since the invention of
the first Bell model, dial-up modems today only require a RJ-45
phone jack to be connected directly to the modem which are
commonly internal located within the computer's case and the basic
user probably never see what a moderm dial-up modem looks like
unless they happen to come across a picture of one.

How a dial-up modem works:

The first step in the process of a dial-up modem connecting to the
Internet, an ISP, or another computer is to clear the phone line by
disconnecting any usage of the phone line that the modem is hooked
up to. Second is for the modem to dial a number using a normal dial
tone and normal tone representing the phone number just as anyone
would do making a regular phone call. Once the modem receives
feedback from the number that it dialed and the feedback comes in
the form of blips and bleeps that lets the modem know that it is in
fact in touch with another modem, the modem then begins the
process of modulation/demodulation which in fact is how the modem
got it's name for the combining of the two terms. After the two
modems exchange greetings and tell each other that each is a
modem, one modem will send a series of analog tones comprised of
highs and lows that represent binary 1's and 0's to a digital
processor. The digital processor then throws along the message in
digital form until it finally reaches the other modem which then turns
the digital signal back into an analog signal of highs and lows, shocks
and no shocks, which it then can translate into 1's and 0's and
therefore using binary code receive the message that was sent. This
process continues back and forth until one side ends the relationship
with the other modem.
Below are two very simple diagrams of this process by following the
dots the series goes along like this: the terminal gives the digital
signal to the modem that then modulates the signal into an analog
signal that can be sent across the phones lines(the telephone world
in this case). Once the analog signal reaches the other modem, that
modem then demodulates the analog signal back into a series of 1's
and 0's represented by shocks and no shocks and thus the one sided
data cycle is completed ending up at the end side computer.