
                           9600 White Paper






                 THE MIGRATION TO 9600 BPS COMMUNICATIONS
                          FOR PERSONAL COMPUTERS 



                         
                         


                    Hayes Microcomputer Products, Inc.
                             705 Westech Drive
                          Norcross, Georgia 30092






INTRODUCTION
 
 
        Whether you look at man's transportation of himself or the 
"transportation" of his information, the trend has always been toward
a faster and more efficient means.
 
        Our trend in communications has enabled us to evolve from 
carrier pigeons and the Pony Express to the telegraph and telephone 
and into microwave and fiber optic data transmission.
 
        Our quest for faster communications continues.




MODEMS AND THE MIGRATION TOWARD INCREASED SPEED AND FUNCTIONALITY
 
        Early modems were not intelligent devices, but simply 
translators which had to be opened prior to each hookup in order to 
rather laboriously set a series of switches that controlled the 
options that configured the modems' operation for the particular 
system they were connected to.
 
        Acoustic couplers, suction cup-like receptacles used with 
telephone handsets, while not as difficult to set up, were prone to 
error because of external noise or vibration.  They also involved 
manual operation of dialing the phone, listening for a special tone 
from the receiving modem, and placing the headset in the coupler.  
This hands-on requirement, of course, eliminated the possibility of 
automated operation and bogged down the communications process.
 
        This unsophisticated environment of the late 1970s was ripe 
for an automated product that could streamline establishing and 
conducting data transmission activities in the Public Switched 
Telephone Network (PSTN).
 


HAYES MODEMS AND THE HAYES STANDARD AT COMMAND SET
 
        Hayes Microcomputer Products, Inc. introduced its innovative 
modem series to fill this void that existed in the communications 
environment.  By providing modems that were both easy to use and 
simple to connect directly to the PSTN, the problems the error-prone 
acoustic connection had been solved.
 
        Using these new modems meant the terminal or personal 
computer operator could control modem functions (such as dialing 
numbers or switching from command to on-line modes) from a keyboard 
or through communications software.  This meant that communications 
had taken a great step forward since operation was now automated and 
repetitive activities (calling an on-line service and automatically 
logging on) could be stored and repeated quickly and more 
efficiently.

        What made the automation possible?
 
        By this time, microprocessors had progressed to a significant
functional level and could provide a means for the modem to execute 
instructions coming from the terminal or personal computer.  Since 
the modem now had the ability to interpret character strings sent to 
it and could respond with result codes, it was easier to control.  
The microprocessor enabled the modem to become a system element that 
was easier to integrate into the computer environment.
 
        The solution to modem control was the Hayes Standard AT 
Command Set.  By taking all of the available standards for the data 
and physical aspects of communications (Bell 103C modulation, RS-232C
physical interface, ASCII data format, and RJ-11 phone connector) and
innovating on top of them, Hayes developed a new industry standard.
 
        The results were the first intelligent modem products to 
        enjoy widespread distribution and use.

 
INCREASED TECHNOLOGICAL ADVANCES
 
        Introduced in 1981, the Hayes Smartmodem 300 implemented the 
Bell 103 telephone signalling standard which uses Frequency Shift 
Keying (FSK).  FSK is limited to lower speeds as a result of band 
width limitations of the voice telephone channel.
 
        True to history, personal computer modem users wanted more. 
Specifically, they wanted more speed with high data transfer 
accuracy.
 
        Modulation techniques were developed to permit increased data
rates.  Phase Shift Keying (PSK) allowed modems to quadruple their 
speed to 1200 bits per second (bps) communications.  This method of 
transmission is considerably more complex than and increased the 
modulation/demodulation capabilities required of the modem.
 
        Both the Hayes Smartmodem 1200, introduced in 1982, and the 
Smartmodem 1200B, introduced in 1983, adhere to the PSK standard 
known as Bell 212A and can communicate with other modems which also 
use this signalling standard.
 
        Users once again demanded more speed and functionality, and 
2400 bps communication implementing Quadrature Amplitude Modulation 
(QAM) was developed.  Higher speeds meant the modems needed more 
sophisticated signal processing circuitry to enable reliable higher 
speed data transfer over the PSTN.
 
        In addition to 2400 bps communication speed, both the Hayes 
Smartmodem 2400, introduced in 1984, and Smartmodem 2400B, introduced
in 1985, included call progress monitoring, adaptive equalization, 
self testing, and the ability to communicate both asynchronously and 
synchronously.

 
EMPHASIS ON INTERNATIONAL STANDARDS
 
        Our evolution into a more global society presents new 
challenges and opportunities for personal computer communications.
 
        The rise in importance of standards setting bodies such as 
the International Telegraph and Telephone Consultative Committee 
(CCITT) is a reflection of the need for the establishment of global 
standards for interconnection of communications equipment.
 
        The work of the CCITT has resulted in the establishment of 
the V.22 and V.22bis recommendations for 1200 bps and 2400 bps 
communications.  Users can confidently purchase modems adhering to 
these standards and be assured that communications with other modems 
(even in foreign countries) applying these standards will be 
compatible.
 
        All Hayes 1200 bps and 2400 bps modems are CCITT V.22 and 
        V.22bis compatible and country-specific models have been 
        approved for distribution in North America, Europe, Central 
        America, the Middle-East, and the Pacific Basin.
 

9600 BPS COMMUNICATION
 
        When data transmission speed for personal computer modems 
accelerated from 300 bps to 1200 bps, the technological hurdles were 
rather lofty.  By comparison, the migration from 1200 bps and 2400 
bps to 9600 bps for dial-up modems was far more complex than the 
earlier advances.
 
        The CCITT V.29 recommendation originally addressed 9600 bps 
communications over four wire leased lines.  At the time of the 
recommendation's drafting, the opinion was that dial-up lines would 
not support 9600 bps communications.
 
        As the quality of transmission lines on the PSTN improved, 
manufacturers began to re-orient the CCITT standard by introducing 
dial-up 9600 bps half-duplex V.29 modems using QAM techniques for 
transmitting data.  This approach for modulation is similar to the 
method used for handling 2400 bps transmission.
 
        Communications equipment manufacturers perceived the need for
full-duplex 9600 bps dial-up modems and the CCITT responded with its 
V.32 recommendation.
 
        V.32 modems are very expensive due to the echo cancellation 
technology the modems require.  Echo cancellation allows the modem to
ignore its own transmission and "focus" itself on the incoming data 
signal from the remote modem during full-duplex transmission.  This 
increases the complexity of the modem and the technology to 
accomplish it is costly.
 
        Additionally, a characteristic associated with personal 
computer data communications applications is one-way communication. 
For example, in downloading a large data file from a mainframe to a 
personal computer, the data flow is essentially in direction.  So, 
V.32 full-duplex capability is not only expensive, but for most 
personal computer data communications applications it is also 
unnecessary.
 
        What, then, are the options for affordable 9600 V.32 
communications?

 
HAYES V-SERIES 9600 BPS MODEMS
 
        Hayes has developed the V-series Smartmodem 9600 and the 
V-series Smartmodem 9600B, 9600 bps half-duplex, fast-turnaround 
modems providing simulated full-duplex V.32 dial-up communications at
a considerably lower price compared to V.32 modems.

        Both modems implement Hayes-exclusive fast turn-around 
technology.  By providing such rapid turn-around of the 
communications link, users receive the benefit of fast data transfer 
through simulated full-duplex at a reasonable cost.  This fast 
turn-around allows data alternately to flow at 9600 bps in either 
direction.
 
        When high capacity is needed in one direction, that direction
gets use of the channel for longer periods.  These periods, however, 
are always short enough that reverse data is not delayed appreciably.

 
TRELLIS CODE MODULATION
 
        Both Hayes 9600 bps modems implement the Trellis Code 
Modulation (TCM) scheme as described in the CCITT V.32 specification 
to add forward error correction to the basic signal.
 
        TCM is especially important as the telephone companies 
continue to implement Adaptive Differential Pulse Code Modulation 
(ADPCM).  ADPCM is a voice signal encoding scheme that allows the 
phone companies to double the channel capacity of digital trunk 
lines.  Unfortunately, V.29 and V.32 modems that use Quadrature 
Amplitude Modulation (QAM) without Trellis Coding will not be able to
communicate successfully at 9600 bps when an ADPCM link is 
encountered.  Modems without TCM will have their speed limited to 
only 4800 bps on ADPCM lines.  The Hayes 9600 bps modems' TCM feature
makes them more readily adaptable to the present and future demands 
and constraints of the PSTN.
 
        TCM can provide up to a four decibel improvement of 
signal-to-noise ratio when compared to a non-TCM scheme such as V.29.
That improvement may appear small, but it provides huge dividends. 
Improving the signal to noise ratio allows a TCM modem to provide 
high quality, reliable communications over dial-up lines that can 
eliminate the need for using costly, conditioned, leased lines for 
9600 bps communications.  This enables the Hayes 9600 bps modems to 
achieve dial-up line performance with that of the Smartmodem 2400 or 
other V.22bis modems.
 

ERROR-CONTROL
 
        Both Hayes 9600 bps modems implement the LAPB link level 
portion of the X.25 protocol for error-control at 2400 bps and 1200 
bps.  CCITT X.25 is a versatile and widely used synchronous protocol 
standard that enjoys popularity as a worldwide standard.  At 4800 bps
and 9600 bps both modems implement an error-control ping pong 
protocol which is an extension of LAPB. Use of this protocol paves 
the way for future Hayes products to continue the migration toward 
the standardized, synchronous communications environment that lies in
the future.

 
ADAPTIVE COMPRESSION
 
        Adaptive Data Compression in Hayes 9600 bps modems typically 
increases the data throughput to speeds of 19,200 bps.  Using a 
Hayes-developed algorithm, data is compressed in real time, 
dynamically adapting to changes in the data being transmitted.

        This operation is transparent to the user and the amount of 
compression that occurs within the modem depends upon the type of 
data being transferred.  Spreadsheet, data, and text files will 
typically flow in and out of the modem at 19,200 bps using the 
standard asynchronous data port.  Other files will also experience 
improved throughput due to data compression between the modems.


AUTOMATIC NEGOTIATION
 
        Automatic Feature Negotiation capabilities in both the 
V-series Smartmodem 9600 and V-series Smartmodem 9600B provide users 
with automatic setup of the error-control link.
 
        During the initial modem "handshake" the local and remote 
modems will connect at the data rate set in the answering modem.  If 
the answering modem is set to a lower speed, the originating modem 
can fall back from 9600 bps to 4800 bps, 2400 bps, 1200 bps, or 300 
bps for maximum flexibility in establishing a connection.
 
        Once the "handshake" is completed, detection of a 
non-V-series protocol device or synchronous-only device at the remote
end occurs.  Then, the negotiation of link parameters such as 
synchronous or asynchronous transmission, asynchronous transparency 
mode, or link address is conducted.  The devices can also coordinate 
the use of X.25 LAPB or Asynchronous Framing Technique (AFT).  AFT is
an asynchronous augmentation for any bit-synchronous protocol such as
LAPB, LAPD, or SDLC.  It the lowest part of the link level of the 
synchronous protocol and brings error-control operation to 
asynchronous transmission links.  Again, an existing standard has 
been built upon to continue the evolution of the communications 
environment.
 

PRACTICAL APPLICATIONS FOR 9600 BPS COMMUNICATIONS
 
        The requirement for more speed is universal and the 
applications for the V-series Smartmodem 9600 and V-series Smartmodem
9600B permeate virtually every area of business.  By combining high 
speed and data compression to improve throughput over an 
error-control link, the Hayes 9600 bps V-series system modems 
continue the company's tradition for providing fast, reliable data 
communications equipment.
 
        By using high speed communications when connecting personal 
computers to corporate mainframes, users can save both money and 
time.  Faster transfer of data means shorter long distance connect 
time and translates quickly into significant dollar amounts.  
Additionally, faster data transfer means better utilization of time 
and shortening the length of time a personal computer is tied to the 
mainframe frees both systems to undertake additional, more useful 
activities.  So, whether the data transferred is a quarterly sales 
report, monthly training schedule, or a credit application for 
processing, 9600 bps error-control communications offers significant 
opportunities to improve efficiency.
 
        Additionally, terminal to mainframe communications can 
expedite functions essential to maximize customer service and 
maintain a competitive edge.  Integrating order entry equipment and 
cash registers into an inventory management system through 9600 bps 
modems can improve an organization's ability to manage inventory and 
ensure proper coordination throughout the distribution channel.
 

THE HAYES COMMITMENT
 
        As the leader in communications hardware and software 
products for personal computers, Hayes has developed its products to 
adhere to the established standards of the industry.  It is our 
intention to do so in the future and to innovate where no standards 
exist to augment the implementation of high speed, advanced 
technology products.  Our commitment to quality, service, and value 
will allow users of Hayes products to benefit from that commitment in
the future as they have in the past.

