FidoNews is the official newsletter of the International FidoNet
Association, and is published weekly by SEAdog Leader, node 1/1.
You are encouraged to submit articles for publication in
FidoNews. Article submission standards are contained in the file
ARTSPEC.DOC, available from node 1/1.
Copyright (C) 1986, by the International FidoNet Association.
All rights reserved. Duplication and/or distribution permitted
for noncommercial purposes only. For use in other circumstances,
please contact IFNA.
Table of Contents
1. ARTICLES
Managing a Major Network Reorganisation
INVITATION TO JOIN A NEW ECHO CONFERENCE - "SOFTWARE CAREERS"
Western New York Net formed
2. COLUMNS
What is Baud Rate
3. WANTED
Writer wanted
4. FOR SALE
Magazine On Disk for IBM PC and Compatibles
DISCACHE V0.01
Buy some MIDI for Christmas!!
5. NOTICES
The Interrupt Stack
LAPTOP echomail
BBS for Whisper Reader/LEX-31 owners
Gary Stern, 155/214 [620/301]
Bill Bolton, 155/219 [620,403]
Managing a Major Network Reorganisation
One of the most frustrating things about being involved in a
"remote" Fido network is finding out how other nets have solved
problems in the past. Somehow or other we manage to struggle
along here on the bottom of the world, often I fear re-inventing
the Fido wheel. Occasionally we come across something that
another net has taken the trouble to document, such as the SOCAL
echomail policy document ECHO-102. Even though this document
was way out of date when I got it, it shed light into several
dim areas of echomail and gave us some idea of what should be done.
In this light I am submitting the documentation on the Great
Australian Network Changeover to FidoNews, in the knowlege that
someone else in the Fido community, either now or sometime in
the future is sure to need to do the same sort of thing again.
I'd also like to say thank you VERY much to Jon Sabol, 1/112, who
turned a spoltlight into many dark recesses of echomail for me.
Bill Bolton
PREPARING YOUR SYSTEM FOR THE
GREAT AUSNET CHANGEOVER
-----------------------------
By Gary Stern
and Bill Bolton
Network 155 in Region 12 will soon cease to exist and will be
replaced by four new networks, Nets 620, 626, 630 and 690 in Region
50. You will need to make some changes to your system to
accommodate the new networks. The way we will pass mail around
the network is also changing. This document will tell you what
you need to do to be ready for changeover day, December 7th.
IF YOU ARE RUNNING FIDO ONLY
----------------------------
Fido users will need these files:
1. XLATLIST.600 Sample control file.
2. ROUTEGEN.60X Sample Control files.
3. AUS_ECHO.ARC New echomail files.
IF YOU ARE RUNNING FIDO + SEADOG
--------------------------------
Fido systems that are also running SEADOG will need an
Fidonews Page 3 29 Dec 1986
additional file:
4. PARTCDOG.600 Sample sections of SEAdog files.
WHERE TO GET THE FILES
----------------------
The files probably wont be ready at the same time that this
document gets distributed but should be ready within a day or
two. A message advising where to get them will follow shortly.
READ IT ALL!
------------
It doesn't matter what you are running, you should read the
whole document before doing anything.
BEFORE THE CHANGEOVER
---------------------
On or before December 1st, 1986.
1) Close down the sending of echomail from your node as
soon as you receive this document. This is done by
disabling all SCANMAIL invocation lines in your RUNBBS
batch files. Then you must edit your AREAS.BBS to remove
all forwarding nodes. You should continue to run TOSSMAIL
after all mail events so that any echomail still in the
mail system that is delivered to you will be tossed to the
correct area.
2) While this point is not policy, you should consider
raising the level of access to your FidoNet MAIL area to
sysop privilege only, until after the changeover.
This will avoid users sending out mail to other nodes with
"soon to be invalid" return addresses. When we change, the
old net numbers will disappear out of the nodelist plus your
individual node within your new net might be different.
Also if you have mail from your system still IN TRANSIT
anywhere in the network (maybe overseas) when the nodelist
with the new node numbers becomes effective, the transiting
node will immediately ORPHAN your messages which means they
will never be delivered.
AT THE TIME TO CHANGEOVER
-------------------------
At 1200 hrs (midday) on Sunday, December 7, 1986:
You should have received NODEDIFF.A39 in the morning mail
Fidonews Page 4 29 Dec 1986
schedule. In a perfect world that would be all you would
receive, however since we haven't had to do a changeover like
this previously you may also receive some final instructions so
please check your mail on that day.
1) Check NODEDIFF.339 with an editor or just type it out, just
to make sure the changes have been done. You will find
that Australia is now in Region 3 which should be well down
toward the end of the file. If for some reason it isn't
there or you haven't received NODEDIFF.A39, DO NOT MAKE ANY
FURTHER CHANGES. Ring your Network Co-ordinator for
information.
2) You will have to modify the new XLATLIST.CTL file
distributed with this document. You need to insert your new
Node Number. If you have any BAUD or PHONE statements
applying to Net 155 nodes statements in your present
XLATLIST.CTL, these need to added and also modified to
reflect the new network addresses. Finally you'll need to
modify the cost table in the new file to suit your
location!
If you are a hub or a host, please carefully read the
special instructions in the XLATLIST.CTL file.
3) ROUTEGEN.CTL must be modified. If you will be in Net 620
you can use the ROUTEGEN.620 file after renaming it to
ROUTEGEN.CTL. If you are in Net 626 use ROUTEGEN.626,
if in Net 630 use ROUTEGEN.630 and if in Net 690 use
ROUTEGN.690. You only have to insert your new NODE number.
You should delete all existing ROUTE.* files before
running Routegen.
4) Before running XLATLIST you must go into Fido and use the
SYSOP "4" command to reset your Net and Node numbers. You
MUST reset your Net/Node numbers before you run XLATLIST.
If you are also a HUB or a HOST you MUST set your Net and
Node number in Fido to your normal node identity. You
should set your Alternate Node number to your hub or host
identity. You MUST NOT put your hub or host identity as
your primary node number.
5) Run XLATLIST and invoke Fido to compile its new nodelist.
6) Modify your RUNBBS.BAT (or SEADOG.BAT) file to cover
the new mail arrangements and external events as detailed
below.
7) Put your system back on line.
NEW MAIL ARRANGEMENTS
---------------------
Fidonews Page 5 29 Dec 1986
Fido doesn't use daylight saving times and will not refer to
them in this document. If you have trouble converting between
Australian Eastern Standard Time and daylight saving time, buy
yourself a cheap digital watch (they just about give them away
now) and leave it set to Australian Eastern Standard time. You
should then be able to get the times right!
The Australian National Mail Hour will run from 0400 to 0500
Australian Eastern Standard Time, 0330 to 0430 Australian
Central Standard Time and 0200 to 0300 Australian Western
Standard Time.
IF YOU ARE IN NET 626, 630 or 690
---------------------------------
Nets 626, 630 and 690 will send mail to their hosts for 25
minutes, starting 30 minutes before the national mail hour using
Schedule-G. Starting 5 minutes after the national mail hour,
nodes will poll their host to pickup mail for 25 minutes using
Schedule-W.
IF YOU ARE IN NET 620 AND ARE A LOCAL NODE
------------------------------------------
Net 620 is more complicated as it running three hubs. The local
nodes will send mail to their hubs for 10 minutes using
Schedule-H, starting 30 minutes before the national mail hour
and ending 20 minutes before the national mail hour. The local
nodes will send any mail not addressed to the nodes on their
hub, and which was not able to be delivered to their hub
(perhaps due to a failure), to the outgate for 10 minutes using
Schedule-G, starting 15 minutes before the national mail hour
and ending 5 minutes before the national mail hour.
After the national mail hour the local nodes will be in a
receive only mode for 20 minutes using Schedule-V. This is
followed by 10 minutes where the local nodes poll their hub for
received mail using Schedule-W.
IF YOU ARE IN NET 620 AND ARE A HUB
-----------------------------------
The Hubs will receive mail from their local nodes for 10 minutes
using Schedule-H, starting 30 minutes before the national mail
hour and ending 20 minutes before the national mail hour. This
is followed by 5 minutes to process the received mail. Hubs
will then send any network mail to the outgate for 10 minutes
using Schedule-G, starting 15 minutes before the national mail
hour and ending 5 minutes before the national mail hour.
The hubs will receive mail from the outgate for 10 minutes using
Schedule-V, starting 5 minutes after the national mail hour and
ending 15 minutes after the national mail hour. This is
Fidonews Page 6 29 Dec 1986
followed by a 5 minutes to process the received mail. For 10
minutes, commencing 20 minutes after the national mail hour, the
hub is polled by its local nodes to pickup received mail, using
Schedule-W.
The 5 minutes between the schedules before and after the national
mail hour are for the hubs to run arcmail (from), tossmail,
scanmail and arcmail (to).
MAIL TIMETABLE FOR HUBBED NETWORK
---------------------------------
The following timetable shows what each stage in a three
tiered mail network (node, hub, outgate) in region 50 does
during national mail processing.
Time Node Hub Outgate
---------------------------------------------------------
0325 Process mail Do nothing Do nothing
0330 Send to hub Receive from Do nothing
nodes
0340 Do nothing Process mail Do nothing
0345 Do nothing Send to Receive from
unless hub outgate hubs
down then
send to
outgate
0355 Do Nothing Do nothing Process mail
0400 Direct mail Direct Mail Poll hosts
if required if required for mail
0425 Direct mail Direct Mail Process mail
if required if required
0430 Direct Mail Direct Mail Send to hosts
if required if required
0500 Do Nothing Receive from Send to hubs
outgate
0515 Do Nothing Process mail Do nothing
0520 Poll hub Hubs hold mail Do nothing
for mail
0530 Do nothing Do nothing Do nothing
0535 Process Mail Do nothing Do nothing
Fidonews Page 7 29 Dec 1986
MAIL TIMETABLE FOR HOST NETWORK
-------------------------------
The following timetable shows what each stage in a two tiered
mail network (node, host) in Region 50 does during national mail
processing.
Time Node Host
------------------------------------------
0325 Process mail Do nothing
0330 Send to host Receive from
nodes
0355 Do nothing Process mail
0400 Direct mail Hold for pickup
if required by outgate
0425 Direct mail Do nothing
if required
0430 Direct Mail Receive from
if required outgate
0500 Do Nothing Process mail
0505 Poll host Hold mail for
for mail nodes
0530 Do nothing Do nothing
0535 Process Mail Do nothing
ECHOMAIL
--------
All echomail will be shut down prior to the changeover. New
software will be distributed to all nodes and echomail
conferences will be reintroduced, one at a time.
To speed mail processing, ARCMAIL is being introduced. ARCMAIL
has a dramatic effect on the handling of all mail, but
especially echomail and will allow us to expand the number of
echomail conferences that can be supported by the network.
Nodes will run an external event commencing an adequate time
prior to their first morning mail period, we recommend at least
5 minutes before the mail period. This event will include
TOSSMAIL to clear any mail echomail left in the net mail message
area for the previous mail time, SCANMAIL to place new echomail
messages from the node into the net mail area and ARCMAIL to
pack the messages for sending.
Fidonews Page 8 29 Dec 1986
Similarly, an adequate time after the morning mail period, nodes
will run another external event, again we recommend 5 minutes
after the end of the mail period to ensure any mail
transmissions have finished. This event will run ARCMAIL to
unpack messages and TOSSMAIL to clear echomail messages from the
net mail areas into the appropriate conference areas. You may
optionally want to renumber or otherwise process received
messages at this stage.
ECHOMAIL CONFERENCES
--------------------
The first echomail conference that will be started is a new one
for the Australian FidoNet Association. This will be followed
by AUST_SYSOP etc. at a later date. You will be advised when
other conferences will individually commence.
The reason for re-starting echomail with a new conference is to
simplify the initial testing of the new echomail routing
structure. When the existing conferences are re-started you
will need to do a lot of work with the SEENBY and SETMARKS
commands to prepare your echomail areas. Instructions on what to
do will be issued separately once we have the AFNA conference
running satisfactorily.
Please note that you must use the new echomail files contained
in AUS_ECHO.ARC. The other conferences will not be restarted
until everyone is using the same versions of echomail software.
You will need to create a system message area for the AFNA
conference and then edit AREAS.BBS to enter the AFNA message
area number and the conference name AUST_FNA.
ECHOMAIL HANDLING
-----------------
Local nodes will only forward echomail to their hubs or hosts.
Hubs or hosts will only forward echomail to their local nodes
plus the outgate.
The following are examples of entries in the AREAS.BBS files for
various nodes:
This hub has the AFNA conference is message area 20 and
forwards it to his local nodes 620/502....620/505 and
to the outgate 620/200
Node 502
--------
Fidonews Page 9 29 Dec 1986
10 AUST_FNA 620/500
This node has the AFNA conference in message area 10
and forwards it to his hub, 620/500 only.
Hubs will still receive messages intended for them as nodes
because echomail knows about alternate node numbers. That's why
its important that your hub or host number be the alternate node
identity and not the primary one.
Using the same examples here are the sort of command lines which
should appear in your RUNBBS batch files:-
HUB 500 before Schedule-G and after Schedule-V
----------------------------------------------
arcmail from 620/200 620/502 620/503 620/504 620/505
tossmail run -stats
scanmail run -nopriv -stats
arcmail to 620/200 620/502 620/503 620/504 620/505
The hub runs the same event for all mail processing.
Before Schedule-G the hub unARCs mail received from its
local nodes and tosses any echomail into the appropriate
areas. It then scans echomail areas for outbound messages,
including any echomail messages originating from the hub.
It then ARCs all mail destined for the outgate and nodes.
Any messages originating on the hub and destined for the
local nodes are ARCed but will remain in the net mail
message area for the time being.
After Schedule-V the hub unARCs any mail received from the
outgate and tosses any echomail into the appropriate areas.
It then scans echomail areas for outbound messages and
places them in the network file area. Any messages for the
local nodes are then ARCed or possibly added to an existing
ARCed packet for the node that was prepared after
Schedule-G.
Note that before Schedule-G there would normally be no mail
from the outgate to be processed, only mail from the nodes.
Similarly after Schedule-V there is normally no mail from
the nodes to be processed, only mail from the outgate.
NODE 502 before and after morning mail period
---------------------------------------------
arcmail from 620/500
tossmail run -stats
scanmail run -nopriv -stats
arcmail to 620/500
The node runs the same event for all mail processing.
Fidonews Page 10 29 Dec 1986
Before the mail period the node tosses any echomail
messages that may have been accidently left in the net mail
message area from the previous mail time. It then scans
the echomail message areas for outbound messages. All mail
for the hub is then ARCed.
After the mail period the node unARCs any mail received
from the hub and tosses echomail into the appropriate
message areas.
To assist in developing a traffic analysis of the network we are
asking all sysops to log statistical information on their
echomail traffic, hence the use of the "-stats" option on
tossmail and scanmail. Please keep archives of these logs as we
will be asking you to forward them so we can get on with the
traffic analysis. The ECHOMSGS.LOG generated by the "-stats"
does not contain any information about the content of the
messages or who sent them, only information on the number of
messages processed out of each echomail area.
To assist in keeping private mail out of echomail conferences we
want you to use the "-nopriv" option with scanmail. This will
stop private "junk" echomail from cluttering up echomail
conference areas.
As ARCMAIL uses a external program to do the ARCing you must
make sure that it is accessible to ARCMAIL by having it in the
same directory or otherwise accessible through a PATH statement
in DOS.
OTHER SCHEDULES
---------------
The ROUTEGEN.CTL you use will also build files for Schedule-R
(Australian National Mail hour) and Schedule-T (International
mail hour) for your convenience. You may wish to edit these
depending on your mail traffic requirements for file attaches
etc.
HELP!
-----
If you don't understand this document (please read it a few times
first to make sure exactly what it is you don't understand) you
should contact the network co-ordinator for your new network.
The new network co-ordinators are :
620 - Brian Gatenby (02) 922-xxxx
626 - Alan Salmon (062) 58-xxxx
630 - John Blackett-Smith (03) 818-xxxx
690 - Leonard Holling (09) 339-xxxx
If your network co-ordinator can't help you to understand it you
can ring REALTORS (02) 387 5335 or SOFTWARE_TOOLS (02) 449-2618
Fidonews Page 11 29 Dec 1986
to leave a message and login again the next morning and collect
your reply.
If all else fails (and we really mean this to be an absolute
last resort, only) ring either Gary Stern (02) 398-xxxx or Bill
Bolton (02) 449-xxxx at home. Please DO NOT EVER publish these
numbers to your users. We can't guarantee to be home but during
the runup period to the introduction to the new network
structure we will definitely try to be after 19:00 AEST.
Just make sure you have contacted your network co-ordinator
first.
SPECIAL NOTES FOR FIDO + SEADOG USERS
-------------------------------------
Setting up for SEAdog is a lot easier than for Fido! In Fido
just set an external event starting at the time of your first
mail event, not 5 minutes before. If you have set your pre-mail
external event to occur 5 minutes before the mail event as we
suggested, this will bring your Fido and SEAdog together as far
as the no answer period just prior to an event. SEAdog has a 5
minutes no answer period while Fido has a 10 minute one.
This external event, which should have the same exit errorlevel
as your " /e" on your FIDOEXEC line. The length of this event
should run till the end of normal morning mail time plus 1
minute. You still have to setup the net/node numbers in Fido
with the sysop 4 command and adjust your XLATLIST.CTL file plus
your ROUTEGEN.CTL file. You will need to change the node
numbers in your CONFIG.DOG file.
Take special note in the XLATLIST.CTL file as there are some
special instructions for SEAdog users in it!
Should you have any problems send a CRASH mail message to
REALTORS (02) 387-5335 but only if you if you have SEAdog up and
running on your board so that you can receive the CRASH reply!!
(otherwise you just wont get a reply).
December 1st, 1986
Gary Stern, Realtors, 155/215 [620/301]
Bill Bolton, Software Tools, 155/219 [620/403]
A new Echo Conference devoted to discussion of various subjects
effecting Software Engineers and MIS professionals has been
started by SuperResume Fido in San Francisco, 125/612,
415-546-0119. SuperResume is operated by Lee Johnson, the
owner of LEE JOHNSON INTERNATIONAL, a recruiting firm
specializing in Software Engineering and MIS Professionals
since 1974. This 12 years of experience seeing candidates
succeed and fail in their professional careers has provided
some very interesting incites. What is needed is a national
forum to discuss these issues and bring together new ideas from
a wide variety of professionals. The proposed Echo Conference
discussion areas are:
The file CARECHO.ARC is available for download on the
SuperResume (tm) Fido (125/625 - 415-546-0119) for those who
would like to participate in all or some of the above AREAS.
It contains and ARC'd BACKUP.COM of all the subdirectories and
dir.bbs's to make installation easy.
In addition to coordinating the SOFTWARE CAREERS ECHO
CONFERENCE, Lee Johnson is also making available his
copyrighted SuperResume (tm) QUESTIONNAIRE.BBS file for Fido
Sysops who wish to run it as the questionnaire feature of their
Boards. It produces a detailed, accomplishment-oriented
resume. This is extremely important because a resume is the
single most important representation of a professional's
career. Many well qualified candidates never even get to first
base (the interview) because they were screened-out due to an
inadequate resume. Nevertheless, most of people only think
about their resume when they are considering changing jobs. As
a result, many deficient, flawed, and poorly constructed
resumes are in circulation today, and many people's growth is
being held back.
Lee Johnson is also offering Fido Sysops A WAY TO DEFRAY A
PORTION OF THE EXPENSE OF OPERATING THEIR BOARDS. If a Board
runs the SuperResume Questionnaire and obtains a completed
SuperResume (or any resume) of a Software Engineering or MIS
Professional candidate, Lee Johnson will pay a $500.00 US
finder's fee to the Sysop and $50.00 US to the National FidoNet
Fidonews Page 13 29 Dec 1986
Administrator if LJI successfully places that candidate. If
the Sysop personally interviews the candidate, and provides a
written appraisal of the candidate, the finder's fee goes up to
ten percent (10%) of LJI's gross fee, which sometimes can be
$15,000, or a $1,500 finder's fee. Detailed interviewing
forms will be supplied if requested.
If you are interested in either participating in the SOFTWARE
CAREERS ECHO CONFERENCE, or in running the SuperResume (tm)
Questionnaire (or both!), please contact Lee Johnson at:
FidoMail 125/612; voiceline: 415-788-6000;
dataline: 414-546-0119.
Bill Hliwa, Sysop
The Med Tech FIDO (260/0, 260/10)
Western New York Net is formed
==============================
Effective with NODELIST.353, the FIDO's of Western New York
will be part of a new network: NET 260. The systems comprising
NET 260 are located in the Greater Buffalo and Greater Rochester
areas. Most members were originally in NET 107; others were
independents in REGION 13.
This reorganization will provide our area with more coherent
communications by directly linking local NET 107 members (who
previously had to deal with New York City -- 400 miles away) and
the local independents. As an added benefit, NY MetroNet (NET
107) should feel some relief from their currently heavy netmail
traffic.
If you send Net Mail (EchoMail) to any of the affected
nodes, please make a note of the change.
For reference, the following nodes are shown with former and
current node designations:
Name Old Net/Node New Net/Node
------------ ------------ --------------
--Buffalo area--
The Med Tech FIDO 13/15 260/10(0)
The IBM Temple 107/701 260/101
I-Tech1 107/703 260/110
AEOLUS 107/713 260/111
GATEKEEPER 107/733 260/112
The Public Domain 13/17 260/120
Anyone reading technical echomail may have noticed a large
number of messages about baud rates, bit rates, band widths, and
modulation techniques involved with modems. There is a fair
amount of confusion relating to baud rate verses bit rate and how
they are limited by the telephone line band width. This is
nothing new, texts on the subject generally avoid the term "baud"
except within the narrow context where it is germane. This
article will define some of the various terms used in data
communications, and discuss limitations of phone lines to
communication speed.
Serial transmission of data is the most common method of
moving data over distance, and the most common way of interfacing
serial devices to each other is RS232. The essence of RS232 is
signal levels which represent ON or SPACE levels, and OFF or MARK
levels. ON is any voltage between +3 volts and +15 volts while
OFF is -3 to -15 volts. The signal shape is really a square wave
centered at zero volts and is a baseband signal. A baseband
signal is one whose spectrum extends down to zero hertz, or near
zero. The signal is polled at regular intervals to determine its
voltage, and therefore the data it contains. RS232 has only the
two voltage levels defined so it is a binary coded signal.
Besides signal shape and levels, RS232 defines a number of
parallel signals such as "clear to send" and "data terminal
ready". Some of these signals are status flags such as "carrier
detect", while others are meant as flow control, such as "data
terminal ready" or "request to send". Since a typical modem
provides only the transmit and receive functions, the flow
control must be done within the data stream. Some modems however
send data as packets with error control (akin to XMODEM) that can
recreate all of the hardware signals so as to make a distant
terminal appear to be hard wired.
Regular phone lines were designed for voice communications,
but due to their wide use and therefore low cost, they have been
widely used for data communications. A baseband signal such as is
found in RS232 doesn't lend itself to phone lines since they
don't have frequency response down to D.C. or zero hertz. When
voice grade phone lines were designed the band of frequencies
they had to pass was determined by the nature of human speech.
Very low frequencies (below 300 hz) and higher ones (above
3000hz) were found to be unnecessary for voice recognition at the
receiving end, as a result the total "BAND WIDTH" available to a
phone user is only around 2700 hz. BAND WIDTH when used to
describe frequency response is the difference in hertz between
the high and low, half power frequencies. In electrical systems,
power dissipated across a load (or resistance) in terms of
voltage is: V * V / R. Where "V" in this case will be the
amplitude of the sign wave being applied to the circuit. In
between the high and low half power frequencies there will be a
Fidonews Page 16 29 Dec 1986
frequency where the amplitude of the response wave will be
maximized, call that voltage Vm. The half power points will be
reached when V=Vm/sqrt(2). The output power at that point would
be Vm * Vm / (2 * R) which is one half the mid band power. The
cause for the fall off of power at different frequencies is due
to capacitive and/or inductive elements in the circuit. In phone
lines capacitance comes naturally in parallel, that is it tend to
shunt the signal to ground. In this configuration the higher the
frequency the lower the "resistance" will be. Inductance is added
on purpose by the phone companies in the form of loading coils
which are added to decrease signal attenuation in the mid
frequencies. In any case the band width of a voice grade line is
strictly limited so that many calls can be stacked on top of each
other, in order to use transmission lines more effectively. Data
equipment must strive to make the best use of this narrow band
width. There is a hard limit to the amount of data that can be
sent through a telephone line as will be seen later.
The signal type of choice to carry data through phone lines
is the sine wave. A sine wave has but one frequency associated
with it. This means that if its frequency is within th band width
of the line carrying it, then the received sine wave will not
have its shape altered due to clipping of the high frequency
components. This can't be said for the square or triangular
waves which requires an infinite band width to fully describe
them. The sine wave is simply defined:
v= A * sin( w*t + p)
A is the amplitude (in units of volts for this exercise)
w is the frequency which must be in radians per second
t is time in seconds
p is the phase angle in radians
Information can be encoded by the sine wave in three
different ways. By altering "A" which is amplitude modulation
(AM), by altering "w" which is frequency modulation (FM), or by
altering "p" which is phase modulation (PM). There are mixed
modes which come into use in the more exotic modem schemes, used
to get the really high bit rates.
FSK or frequency shift keying was the most widely used
method for data transfer through modems. This is a FM process
whereby a RS232 MARK would be represented by the presence of one
frequency while a SPACE would be indicated by another frequency.
Now is the time to introduce the term BAUD. A "BAUD" is the time
interval in which data is carried, that is the minimum time in
which a signal holds a single state which the receiver is to
recognize and convert into data. The baud rate is how many BAUD
times occur in a second. The baud rate is NOT the same as the bit
rate as will be seen later in multiple state modulation. In FSK
type modems (Bell 103) the baud time happens to be the same as
the bit rate since each signal state encodes a single bit. Many
would think that the baud rate is limited to highest frequency
available to be transmitted (3000 hz) but this is not necessarily
so. Nyquist showed in 1928 that the maximum signal change rate
(baud rate) for a band width "W" would be 2*W baud. This is
Fidonews Page 17 29 Dec 1986
called the Nyquist rate and is an upper limit that assumes no
inter-symbol interference. This could be visualized by
considering a sine wave. Each cycle has a positive and negative
part. The amplitude in each part could be independently altered
while still having a sine wave, therefore a 1200 hz signal could
be changed 2400 times a second which is 2400 baud. This type of
change (AM) is not very useful in phone lines since it is the
type of change most commonly caused by natural phenomena. In Bell
103 the baud rate is commonly 300 which is over 3.5 cycles at the
lowest carrier frequency. The practical considerations of
detecting frequency changes requires about 1.5 cycles so 300 baud
is some what conservative.
PSK or phase shift keying gets by the frequency barrier that
keeps FSK from producing the higher bit rates. In PSK (a PM
method) the only parameter in the sine wave changed each BAUD is
the phase angle "p". The Bell 212A modem specification uses a
four level phase modulation technique. The term four level means
that four different phases are used and detected by the receiver
during each BAUD. The number of bits an M level state can
represent is n=log2(M) or log(M)/log(2). A four level state can
represent two bits during each baud. In the 212A specification
+90 degrees would be 00, 0 degrees 01, +270 degrees 11, and +180
degrees 10. The 212A baud rate is 600 which means the bit rate
would be:
bit rate=600 BAUD/second * 2 bits/BAUD= 1200 bits/second
To increase the bit rate to the next state would require 3
bits/baud or 8 phases. To get 2400 bps using such a scheme would
require 16 different phases (22.5 degrees apart). The problem
here is that one class of noise present in phone lines called
"phase jitter" can cause phase errors up to and sometimes over 30
degrees. To avoid the bulk of this type of noise the phase angle
difference should be kept above this amount. The 2400 baud modems
common today use a form of QAM (quadrature amplitude modulated).
This method uses a combination of two waves with different
amplitudes to get the required 16 levels. A QAM signal can be
expressed in equation as follows:
s(t)=a(t)cos(wt+p)+b(t)cos(wt+90+p)
a(t) is the in-phase modulating wave form while b(t) is the
quadrature modulating wave form. During each baud a(t) and b(t)
are constants so the equation simplifies to:
s(tn)=c*cos(wt+theta+p) {p is a single arbitrary phase angle tn
stands for a specific baud time
c=sqrt(a*a+b*b) theta=atan(b/a)}
The new pure sine (cosine) wave has amplitude and phase
differences which can multiply the number of states possible. If
there are 4 values for amplitude and 8 values for phase then the
signal could have 32 different states or five bits. The random
variations in phase "p" has less effect the outcome since it
effects both waves the same. The phase difference in the
Fidonews Page 18 29 Dec 1986
resultant wave is due to the interaction of the two wave forms.
QAM is the method used to get up to 9600 baud out of a phone
line. Other types of noise are present in a phone system, and are
mostly due to switching and cross over with other wires. The
error rate at the higher bit rates would be unacceptable if there
weren't some error recovery used. This is now quite easy to do
from a hardware standpoint, since the memory and processing power
needed to do it takes a small amount of space and cost little
enough to make the increase in bit rate worth it. The ability
for high speed modems to run will increase due to another reason.
More and more fiber optic phone line will replace conventional
ones. These are immune from many of the noise sources that effect
copper wires, sources such as RF and magnetic fields.
The ultimate bit rate that could be "pumped" through a phone line
is fixed by the band width AND the signal to noise ratio.
Shannon's law relates random bit transmissions/second to band
width and signal to noise ratio. It is derived from the concept
of entropy. Entropy is a measure of randomness in a system. It is
really a thermodynamic property but has applications in
information theory. The maximum bit rate for a channel with
signal power S and noise power N is given by:
C=BW log2(1+S/N) where BW is the band width, S is the signal
power and N is the noise power.
With a typical band width 2600 hz and a typical signal to noise
ratio of 30db (or 1000/1) the bit rate would be:
bit rate=2600 * log2( 1001 ) or 25,914bps
The noise factor is assumed white or Gaussian. This kind of noise
is unavoidable in electrical systems. In fact "N" can be
calculated by:
N=kTW where k=1.37e-23 joule/degree
T is absolute temperature (Kelvin)
W is the band width in HZ
This product gives "N" in terms of joules per second or watts.
At room temperatures noise would be on the order of 1e-17 watts
over a 2600 hz band width. If a phone signal were just 0.1 watts
the signal to noise ratio could be as high as 160db. In practice
it is about 30db so it can be expected that the signal to noise
ratio will increase in the future so that the top bit rates will
increase, and this increase will happen without an increase of
the band width available.
One last problem to consider with the high speed modems is
compatibility. To get 9600 bps from a 600 baud signal would
require 65,536 levels in a state. There is no obvious way in
which to assign a level to a 16 bit pattern so the manufacturer
must invent an "ALPHABET" for that conversion. Until an alphabet
is standardized as well as error recovery techniques there is
simply no way the modems will talk to each other.
Fidonews Page 19 29 Dec 1986
GLOSSARY:
Alphabet: A table to convert signal states into
characters they represent
Amplitude modulation: Where information is encoded by changes in
amplitude only.
Band width: Range of frequencies within the half power
limits. That is the difference between the
two -3db frequencies.
Baseband: The signal at its original frequency and
shape.
Baud: The minimum time where all signal
parameters are held constant.
Baud rate: The number of times the basic signal can be
changed per second.
Bit rate: The number if bits per second passing
through a channel. In a modem it is the
baud rate times the number if bits per
baud.
Decibel (db): 10 * log10(p2/p1) where p2 is referenced to
p1. Both p1 and p2 represents power. For
voltage db is calculated 20 * log10(v2/v1)
Frequency modulation: Where information is encoded by changes in
the carriers frequency.
FSK: A way of represents data by a discrete
change in frequency of the carrier.
Hertz: Number of events per second.
Modulation: The process of varying a signal according
some aspect of another signal.
Phase: The angular displacement of a cyclic signal
In a sine wave Y=A sin(wt+p) p is the
phase.
Phase modulation: Technique of changing phase of signal to
represent changes of the baseband signal.
References:
1.*Clark, A.P., 'Principles if Digital Data Transmission' 2nd ed.
(1983)
2. Martin, James, 'Telecommunications and the Computer', (1979)
3. 'IBM PC Technical Reference', (July 1982)
4. 'Hayes Smartmodem 1200 manual'
*Reference (1) gives the most technical detail and over 500 other
specific references.
Hi! I'm the Technical Editor for a new Hong Kong based
magazine,and I'm looking for someone, or someones, to write a
regular column on the North American computer scene.
What we're looking for is something a lot like Jerry Pournelle's
Chaos Manor in Byte (you can take that as a compliment, Jerry, if
you come across this), with coverage of events, conferences, new
products, etc. Since we can't, yet, offer Byte's kind of money or
expenses, we really need someone who is working in the field,
gets around, can write and wants to earn some extra money. Most
of the time you'll decide for yourself what you want to cover.
Occasionally we'll ask you to do something specific.
We're also open to receiving articles on a one-off basis,
including reviews, programs etc. We'll pay on a sliding scale,
according to how much editing is needed, for text, photos and
programs.
All submissions should be supplied on IBM compatible disk. In the
case of programs they should be heavily annotated, and public
domain (they'll all be posted on SEAnet, our local Fido host).
IBM, Mac and Unix-based programs are more likely to get into
print, the Amiga and Atari STs are not available here. Obviously
Mac programs should be on a Mac disk (although we'd still prefer
the text in IBM format if possible, we don't yet have an in-house
Mac).
If you are interested, or you know someone else who is, I can be
reached by mail at:
=================================================================
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=================================================================
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The first issue of BIG BLUE DISK, a magazine on disk for the IBM
Personal Computer and compatibles, will hit the stands this
October. It is contained entirely on a floppy disk. Each issue
contains programs, articles, feedback from subscribers, program
reviews and demos, and more.
For example, issue number one contains the following:
- PLANET OF THE ROBOTS: In this text adventure, a time warp has
transported you to a future Earth where robots rule. Can you
find your way back?
- HOP-A-LONG HANGMAN: A new version of the classic word game,
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- LIFETIME CALENDAR: Travel back in time or plan the future.
Display any month from January, 1753 to December, 4999.
- LOAN AMORTIZATION: Calculate simple interest loan terms that
best suit your budget. This easy-to-use program produces a
full amortization schedule.
- STRING ART: This program generates many captivating patterns.
Check it out; a little high-tech cloud watching is good for the
soul.
In addition, BIG BLUE DISK #1 contains a column of hints and
tips; and a report of late-breaking news in the computer
industry. Also, for the first time anywhere, BIG BLUE DISK
presents a review of VersaForm XL version 4.0, the latest version
of an inexpensive but powerful, programmable, forms-oriented
database.
This issue will be available at many outlets nationwide,
including Waldenbooks and B. Dalton Booksellers. You can also
order it by direct mail by sending $9.95 (check, money order, or
Visa/Mastercard/American Express accepted) to: BIG BLUE DISK, PO
BOX 30008, SHREVEPORT, LA 71130-0008.
Mail subscriptions are also available: One year (12 monthly
issues) costs only $69.95. (A 41% savings over newsstand price.)
A six-month subscription is available for $39.95.
BIG BLUE DISK requires an IBM PC or compatible, with at least
256K of memory and a Color Graphics Adapter or compatible
graphics board. Send questions/comments to Daniel Tobias on FIDO
19/216.
Are you dealing with a large Database that takes forever to read?
Is your Network bogged down due to disk seek time? Do you simply
want to make BETTER use of the EXTENDED OR EXPANDED memory
capacity on your system?
Your solution is:
D I S C A C H E V 0.01
DISCACHE can help you recover lost seconds when it counts!
DISCACHE works by keeping commonly accessed disk data in memory
so that when such data is read it is copied from memory rather
than read from disk.
DISCACHE supports 3-types of memory:
1. CONVENTIONAL (to 640K)
2. EXTENDED - AT memory via BIOS INT 15
3. EXPANDED - via Lotus/Intel EMS
DISCACHE can help you utilize ALL of your Extended/Expanded
memory to the fullest, as it helps you get the most from your
system.
DISCACHE is available NOW, not for the full price of $99.00, but
for a LIMITED TIME at $49.00 (Through Dec 31st, 1986)
HOW DO I GET DISCACHE? Simply write to:
WEG Systems, P.O. Box 5072, Springfield, VA 22150.
HOW DO I GET MORE INFORMATION? There are 2-ways to obtain more
information: Write to us at the address above -OR- Call us via
MODEM (with your computer) to our support line at (703)-425-0695,
WAFRUG_BBS, (1200/300 baud) 24hrs daily, 7-days weekly.
Systems Design Associates' PROMIDI(tm) Studio System SDA-200.
The SDA-200 Promidi Studio System consists of the Midicard and
associated software for an IBM Personal Computer or Compatible.
PROMIDI RECORDS MIDI MUSIC DIRECTLY TO DISK IN REAL TIME:
Recording length and number of recordings/tracks limited only by
disk space. Real-time recordings of 60,000 notes with a 2-drive
system, 1.5 million with a 10Meg hard disk, with only 256K of RAM
in the host computer. PROMIDI'S ONLY LIMIT ON STORAGE IS DISK
SPACE.
PROMIDI LETS YOU RECORD IN FILES, RATHER THAN TRACKS: Promidi
FILES EACH SUPPORT ALL 16 MIDI CHANNELS. You can edit, extract
or copy individual MIDI channels in a file, even move MIDI music
from one channel to another. Further, with the new Midimerge,
Promidi users can record up to EIGHT MIDI INSTRUMENTS IN A FILE
AT ONCE WITH NO LOSS OF FIDELITY yet edit them individually, just
as if they had been recorded one-at-a-time.
PROMIDI'S RESOLUTION IS 192 CLOCKS PER BEAT AT ALL TEMPOS:
PROMIDI SOFTWARE IS DOWNLOADABLE: All operating instructions for
the Midicard interface are part of the Studio System recording
software. The absence of PROM chips on the interface ELIMINATES
chip-changing,and incompatibility caused by MULTIPLE HARDWARE
VERSIONS.
PROMIDI GIVES YOU MORE POWERFUL EDITING TOOLS: Automated
Punchin/Out, Cut & Paste, MaxAuto quantizing, Scalewise &
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BUILT-IN FSK TAPE SYNC and METRONOME, plus a ONE-YEAR WARRANTY on
both hardware and software. And more products compatible with
Promidi are in the works.
MidWest MIDI and SDA offer a 30 day money back gaurantee to all
mailorder customers, if not completely satisfied with the PROMIDI
System. Try before you buy DEMO program disk are also available.
More information about PROMIDI and the other brand name MIDI
products for the Commodore AMIGA,64/128, ATARI ST, APPLE //,& MAC
is available online on MidWest MIDI BBS (405) 733-3102 - 147/6 -.
17 Jan 1987
Deadline for voting on the proposed bylaws. Your ballot MUST
be received by this date!
17 May 1987
Metro-Fire Fido's Second Birthday BlowOut and Floppy Disk
Throwing Tournament! All Fido Sysops and Families Invited!
Contact Christopher Baker at 135/14 for more information.
24 Aug 1989
Voyager 2 passes Neptune.
If you have something which you would like to see on this
calendar, please send a message to FidoNet node 1/1.
The LAPTOP echomail conference deals with the TRS-80 Model 100,
102, 200, and other such laptop computers (but not the IBM PC
portables). If you are interested in joining this conference,
please contact the nearest of Fido 138/14, Fido 115/100, or Fido
11/301.
We are looking for anyone who has purchased a Whisper Reader
portable data terminal being liquidated by MPC Sales, or who may
own an original LEX-31, both manufactured by Lexicon. Whisper
Line is a BBS set up for owners of these terminals to exchange
tips and techniques. Give us a call!
*Official IFNA By-laws Ballot
Official IFNA Articles of Association and By-laws Ballot
We, the interim directors of IFNA, submit for ratification the
Articles of Association and By-laws as published in FidoNews
number 349. In accordance with the recommendation of the By-laws
Committee, each person listed as the Sysop of one or more FidoNet
nodes, as of NODELIST.311 dated November 7, 1986, is entitled to
ONE vote.
The proposed IFNA Articles of Association and By-laws, as
published in Fido349.NWS dated December 22, 1986, should be:
(Check one line) Adopted ________
Rejected ________
I am the SYSOP of record a FidoNet node which was listed in
NODELIST.311 dated November 7, 1986 and have the right to cast
one vote. There will be ONLY be one vote per person. There will
be ONLY one vote per net/node number. I understand these rules
and cast my ballot in accordance with them.
_______________________ ___________
Signature Date
_____/______
Net Node
Return this ballot via U. S. Mail to arrive not later than
January 17, 1987 at:
IFNA Ratification
C/O Christopher L. Bonfanti, CPA
Aselage, Kiefer & Co.
701 Emerson Road, Suite 201
Creve Coeur Corporate Center
St Louis, Mo. 63141-6709
Aselage, Kiefer & Co. are Certified Public Accountants and will
provide an independent count of the vote and publish the results
in FidoNews. Votes received by Saturday, January 17th will be
included in the results.
