Computer Networking Concepts Modems Modems A modem is

Modems A modem is a Modulator/Demodulator, it connects a terminal/computer (DTE) to the Voice

Basic Definition • The modem (DCE - Data Communication Equipment) is connected between the

Digital Connection • The connection between the modem and terminal/computer is a digital connection.

Digital Connection The control lines determine: whose turn it is to talk (modem or

References Introduction to Data Communications Copyleft Sept. 1999 - Jan 2005 TCP/IP Tutorial and

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Computer Networking Concepts: Modems

Modems A modem is a Modulator/Demodulator, it connects a terminal/computer (DTE) to the Voice Channel (dial-up line).

Basic Definition • The modem (DCE - Data Communication Equipment) is connected between the terminal/computer (DTE - Data Terminal Equipment) and the phone line (Voice Channel). • A modem converts the DTE (Data Terminal Equipment) digital signal to an analog signal that the Voice Channel can use. • A modem is connected to the terminal/computer's RS 232 serial port (25 pin male D connector) and the outgoing phone line with an RJ 11 cable connector (same as on a phone extension cord). • Male connectors have pins, female connectors have sockets.

Digital Connection • The connection between the modem and terminal/computer is a digital connection. • A basic connection consists of a Transmit Data (TXD) line, a Receive Data (RXD) line and many hardware hand-shaking control lines.

Digital Connection The control lines determine: whose turn it is to talk (modem or terminal), if the terminal/computer is turned on, if the modem is turned on, if there is a connection to another modem, etc. .

References Introduction to Data Communications Copyleft Sept. 1999 - Jan 2005 TCP/IP Tutorial and Technical Overview An IBM Redbooks publication Published 19 December 2006 Computer Networking: A Top-Down Approach (7 th Edition) James Kurose & Keith Ross