Modem is any type of data communications equipment (DCE) that enables digital data transmission over the analog Public Switched Telephone Network (PSTN). The term “modem” (which actually stands for “modulator/demodulator") is usually reserved for analog modems, which interface, through a serial transmission connection such as the RS-232 interface, with data terminal equipment (DTE) such as computers. The modem converts the digital sign coming from the computer into an analog signal that can be carried Over a Plain Old Telephone Service (POTS) line. The term “digital modem” is sometimes used for ISDN terminal adapters, but this is something of a misnomer because no signal modulation actually takes place.
Modems generally have two interfaces:
Modem types include the following:
Modems generally have two interfaces:
- An RS232 serial transmission interface for Connecting to the DTE, usually the computer
- An RJ-11 telephone interface for connecting to the 4-wire PSTN telephone outlet in the local loop connection
- The USB Modem is a compact external modem that interfaces with computer via a USB port. The modem is ideal for Apple users who own a computer without an internal modem and use a dial-up connection to connect to the internet. The modem can connect at speeds of up to 56 kbps using the V.92 protocol. Its compact form factor makes it ideal for notebook computer Users who find themselves on the road and need to dial-in to an office network or for home users who simply need to add an unobtrusive modem to their computer.
Modem types include the following:
- Internal modems, which are Installed as interface cards inside the computer and might use some of the machine’s CPU processing power for functions such as encoding and data compression.
- External modems, which are generally more expensive and connect to the serial port on the computer using a DB9 or DB25 connector. External modems are useful when several users need to share a modem.
- PCMCIA modems, which are credit-cards-sized modems for laptop computers used by mobile workers.
- Voice/data/fax modems, which can be used for file transfer, sending voice mail using associated software.
Post a Comment