Is a short form for Modulator/Demodulator
The process of converting binary information into analog signals is called modulation and process of converting analog signal back to binary information is called demodulation
Enables a computer to transfer data over the telephone or cable lines
Transmission speed – high data transmission rate can be achieved by compressing the data
Voice or Data communication
Data compression – if the modem is trying to compress data that is already compressed, the compression will be less efficient
Auto answering
Fax capability
Software in computer activates modem, which listens for dial tone on phone line
Modem dials a specified number
Modem at receiving end answers call and sends out a signal
Modem at sending end converts digital signals to analog signals
Modem at receiving end converts analog signals back to digital signals
Internal - A modem card that you can plug into an expansion slot on the motherboard. It is advisable to remove the telephone line when not used
External - Connected to the PC through a cable, which is plugged into serial port on the back of the system unit.
X2 Modem – US robotics developed X2 technology to transmit data at the speed of 56 Kbps over plian old telephone service (POTS). Limitations: DTR is 40kbps from your computer to dial up server and ISP modem must support V.90 standard
V.90 Modem - Built with an assumption that one end of a modem session has a pure digital connection to the telephone line and DTR is 56 kbps
ISDN Modem - Enables to send data, voice, and video over digital telephone lines or over an ordinary telephone wire. DTR is 64 kbps and requires ISDN adapter to perform conversion between digital and analog signal
DSL Modem - Carries both voice and data at the same time. It’s a high speed connection that allows the phone wires to transmit modulated digital content at high speed
Cable Modem – Transfers data much faster than the regular telephone modems, ISDN modems, and DSL modems. External cable modem is connected to either Ethernet card or USB port on the computer. Communicates with a Cable Modem Termination System (CMTS) at the local cable TV company office
Two modems communicating with each other must support same modulation standards
Best Practices
Precautions
To solve the problems that might arise due to modem itself or due to communication software such as auto dialer or dial up connection
