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13g. Modem Speeds / Standards

Bell 103	300 bps FSK -Half duplex
Bell 113	300 bps FSK - Full duplex
Bell 202	1200 baud half duplex
Bell 212A	1200 bps DPSK (Dibit Phase Shift Keying) - V.22 compatible 300 bps FSK (Frequency Shift Keying) - NOT V.22 compatible
MNP1-3	Microcon Networking Protocol - Basic error detection and control of errors.
MNP4	Error correction + adapts to line conditions.
MNP5	Error correction + adapts to line conditions and adds Compression technique used to double the data transfer rate.
RS-232D	Cable and connector standard
V.22	1200 bps DPSK (Dibit Phase Shift Keying) - Bell 212A compatible 600 bps PSK (Phase Shift Keying) - NOT Bell 212A compatible
V.22bis	2400 bps - International Standard Fallback in Europe to V.22 Fallback in America to Bell 212A
V.24	European Mechanical specifications for RS-232D
V.26 .	Synchronous 2400 bps modem 1200 bps DPSK full duplex
V.27	Synchronous 4800 bps DPSK modem
V.28	European Electrical specifications for RS-232D
V.29	Synchronous 9600 bps QAM
V.32	9600 bps QAM
V.32bis	14.4 Kbs QAM1
V.33	14.4 Kbps Trellis Coded Modulation for noise immunity.
V.34	28.8 Kbps modem standard
V.34bis	33.6 Kbps modem standard
V.42bis	Compression technique to roughly double the data transfer rate. Uses Automatic Repeat Request ARQ and CRC (Cyclic Redundancy Checking)
WE201	Synchronous Western Electric 2400 bps DPSK
WE208	Synchronous 4800 bps DPSK
WE209	Synchronous 9600 bps

13h. Transfer Rate versus PC Bus Speed

The lowliest XT PC can out-perform the fastest modem transfer rate. For example: an XT has an 8 bit parallel expansion bus operating at 4.77 MHz. This equates to a data transfer rate of:

Compare this to the fastest modem transfer rates of 57.6 kbps!

Introduction to Data Communications
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