Agilent Technologies Auroraduet N1726A, User Manual, Page: 359 / 507

aurora
Duet
- User Guide
7 - 52 422685
Standards for Modems
International standards for modems exist in the form of
ITU-T V series recommendations. These standards have
been adopted in both European and, to a lesser degree,
North American PTTs. Various other proprietary
standards have also emerged for features such as data
compression and error correction.
External versus Internal Modems
A modem may be either an external, stand-alone device
or it may be internally built into the PC's adaptor card.
Internal modems may also take the form of a Modem PC
card (PCMCIA) which can be slotted into a computer,
usually a laptop.
External modems require their own power supply,
whereas internal modems (including the PC card type)
take their power from the PC. Cabling needs constitute
another significant difference between internal and
external modems; both types of modem need a
connection to the telephone line, however only the
external modem requires cabling to the PC via the serial
port.
Another advantage of using an internal modem is that
you do not require a high speed serial port. Internal
modems have their own UART (Universal Asynchronous
Receiver/Transmitter); with external modems the UART
is on the serial board.
Chap7s3.PM6 17/06/99, 09:52 52