Modems and Fax Boards - Bell, MNP and CCITT

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Bell, MNP and CCITT

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Bell 103 And 212A (American Bell Standard)
Bell 103 and 212A are North American standards that specifies the way modems transmit information.

Version 103 applies to asynchronous modems transmitting at speeds up to 300 bps.
Version 212A applies to full duplex asynchronous or synchronous modems that transmit at speeds up to 1200 bps.

MNP (Microcom Networking Protocol)
Provides error control and data compression when your modem is communicating with another modem that supports MNP. (MNP classes 1 through 4 are specified by CCITT V.42 as a backup error control scheme for LAPM.) Your modem supports five MNP classes. Each MNP class has all the features of the previous class plus its own.

MNP class 1 (also called block mode): Sends data in one direction at a time. About 70 percent as fast as data transmissions using no error correction.
MNP class 2 (also called stream mode): Sends data in both directions at the same time. About 84 percent as fast as data transmissions using no error correction.
MNP class 3: Sending modem strips start and stop bits from data block before sending it. Receiving modem adds start and stop bits before passing the data to the receiving computer. About 8 percent faster than data transmissions using no error correction.
MNP class 4: Monitors the quality of the connection and streamlines the information in the headers of data blocks. If the telephone line is relatively noise-free, the modem sends larger blocks of data to increase throughput. If the telephone line is noisy, the modem sends smaller blocks of data so that less data will have to be resent. This means more successful transmissions on the first try. About 20 percent faster than data transmissions using no error correction.
MNP class 5: Provides data compression. Sending modem detects redundant data and recodes it to fewer bits to increase the effective throughput. Receiving modem decompresses the data before passing it to the receiving computer. Up to 100 percent faster than data transmissions using no data compression or error correction, depending on the kind of data transmitted. (Files that are already compressed will seem to contain less redundant data and may therefore take longer to transmit using MNP class 5 than they would if you were using no data compression.)

Bell Standards Supported By Intel Modems
Intel modems support these Bell specifications:

All Intel
Modems
103 *
212A *

MNP Standards Supported By Intel Modems

Intel modems support these MNP specifications

MNP Class	V.42bis Modems(1,2)	MNP Modems(3)	non-MNPModems(4)
1	*	*
2	*	*
3	*	*
4	*	*
5	*	*

CCITT STANDARDS SUPPORTED BY INTEL MODEMS

Intel modems support these CCITT specifications:

	SatisFAX./, 350,14.4EX	Satis-9600EX	Satis-FAXtion	2400EX	SatisFAX./ 100,2400B	CCP
V.21	*	*	*	*	*	*
V.22	*	*	*	*	*	*
V.22A	*	*	*	*	*	*
V.22B	*	*	*	*	*	*
V.22bis	*	*	*	*	*	*
V.24	*	*		*
V.32	*	*
V.32bis	*
V.42	*	*
V.42bis	*	*
V.54	*	*	*	*	*	*

Ccitt Standards Descriptions

CCITT (Consultative Committee for International Telephone and Telegraph) is an international committee that specifies the way modems and fax machines transmit information to ensure compatibility among modems.

Note:
The suffix "bis" designates the second version of a particular standard.

CCITT V.1	Defines binary 0/1 bits as space/mark line conditions
CCITT V.2	Limits power levels of modems used on phone lines
CCITT V.4	Sequence of bits within a character as transmitted
CCITT V.5	Standard synchronous signaling rates - dial-up lines
CCITT V.6	Standard synchronous signaling rates - leased lines
CCITT V.7	List of modem terms (in English, Spanish, French)
CCITT V.10	Unbalanced high-speed electrical interface characteristics (RS-423)
CCITT V.11	Balanced high-speed electrical characteristics (RS-422)
CCITT V.13	Simulated carrier control (full duplex modem used as half duplex)
CCITT V.14	Asynchronous to synchronous conversion
CCITT V.15	Acoustic couplers
CCITT V.16	Electrocardiogram transmission on phone lines
CCITT V.17	Application-specific modulation scheme for Group 3 fax (Provides 2-wire half-duplex trellis-coded transmission at 7200, 9600, 12000, and 14400 bps.
CCITT V.19	DTMF modems (low-speed parallel transmission)
CCITT V.20	Parallel data transmission modems
CCITT V.21	300 bps modems
CCITT V.22	1200/600 bps FDX modems
CCITT V.22bis	2400 bps modems
CCITT V.23	1200/75 bps (host tx 1200, rx 75, terminal tx 75, rx 1200). Also supports 600bps in the high channel speed. V.23 is used in Europe to support some videotext applications. Intel modems do not support the V.23 standard.
CCITT V.24	Known as EIA RS-232 in the USA. V.24 defines only the functions of the circuits. EIA-232-E (which is how the current version of the standard is designated) also defines electrical characteristics and connectors. The 232-equivalent electrical characteristics and connectors are defined in ISO 2110
CCITT V.25	Automatic answering equipment and parallel automatic dialing (defines the 2100Hz "answer tone" that modems send)
CCITT V.25bis	Serial automatic calling and answering -- CCITT equivalent of AT commands (This is the current CCITT standard for modem control by computers via serial interface. The Hayes AT command set is used primarily in the USA.)
CCITT V.26	2400 bps 4W modems
CCITT V.26bis	2400/1200 bps HDX modems
CCITT V.26ter	2400/1200 bps FDX modems
CCITT V.27	4800 bps 4W modems
CCITT V.27bis	4800/2400 bps 4W modems
CCITT V.27ter	4800/2400 bps FDX modems (Also used in half-duplex 2-wire mode to implement the 2400 and 4800 bps transmission schemes in Group 3 fax.)
CCITT V.28	Electrical characteristics for V.24
CCITT V.29	9600 bps 4W modems (Also used in half-duplex 2-wire mode to implement the 7200 and 9600 bps transmission schemes in Group 3 fax.)
CCITT V.31	Older electrical characteristics (rarely used)
CCITT V.31bis	V.31 using optocouplers
CCITT V.32	9600/4800 bps FDX modems
CCITT V.32bis	4800, 7200, 9600, 12000, and 14400 bps modems and rapid rate renegotiation
CCITT V.33	14400 bps (and 12000 bps for 4-wire leased lines)
CCITT V.35	48 kbps 4W modems(The CCITT no longer recommends the use of this standard. It was made obsolete by V.36.)
CCITT V.36	48 kbps 4W modems
CCITT V.37	72 kbps 4W (V.36 and V.37 are not really "4w modems." They are group band modems, which means they combine several telephone channels.)
CCITT V.40	How teletypes indicate parity errors
CCITT V.41	An older, obsolete error control scheme
CCITT V.42	Error correcting procedures for modems using asynch-to-synch conversion (V.22, V.22bis, V.26ter, V.32, V.32bis); defines LAPM protocol and provides fallback to MNP4
CCITT V.42bis	Lempel-Ziv-based data compression scheme for use with V.42 LAPM
CCITT V.50	Standard limits for transmission quality for modems
CCITT V.51	Maintenance of international data circuits
CCITT V.52	Apparatus for measuring distortion and error rates for data transmission
CCITT V.53	Impairment limits for data circuits
CCITT V.54	Loop test devices for modems
CCITT V.55	Impulse noise measuring equipment
CCITT V.56	Comparative testing of modems
CCITT V.57	Comprehensive test set for high speed data transmission
CCITT V.100	Interconnection between PDNs and PSTNs (Public Data Networks, Public Switched Telephone Networks)
CCITT V.110	ISDN terminal adaption
CCITT V.120	ISDN terminal adaption with statistical multiplexing
CCITT V.230	General data communications interface, layer 1

This applies to:

Modems and Fax Boards

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Solution ID: CS-011464
Date Created: 18-May-2004
Last Modified: 19-Nov-2008