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Background Communications program. Download in background.
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Background Communications program. Download in background.
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THE INVISIBLE LINK

Copyright (C) 1987
Robert Best and Garland Wong
Santa Ana, CA and La Jolla, CA
All Rights Reserved

I. ABOUT INVISIBLE LINK

The Invisible Link is a general purpose asynchronous communications
program. However, it differs from an ordinary communications program in
that the Invisible Link is memory-resident and designed to function as a
background task executing concurrently with any MS-DOS application
program. This means you can dial or transfer files in the background
without tying up your computer system. Imagine, you can simultaneously be
working in your favorite word processor or spreadsheet and still be
dialing a busy number or receiving those important files. Best of all,
you won't even notice that IL is running or "doing its thing". In terms
of time savings alone, IL will "pay for itself" during its first hour of
use. IL was written in assembly language for optimum size and speed. It
represents the result of a thorough six month period of development and
testing. It has proven to run faster and more reliably than the
competition (who charge from $100 - $200 for their product), as any
thorough benchmarking will testify. When you are transferring a file in
the background, there is no noticeable degradation in your foreground
application program. Lastly, you can use IL's background transfer or dial
capability along with your favorite communications program. This means
you don't have to give up your favorite communications program because IL
was designed to work within or along side them.

The Invisible Link has the following features:

- Communicate at speeds up to 9600 baud (limited by the speed
of your serial port and modem.)

- Exchange binary or text files in the background using
Xmodem CRC or Xmodem Checksum Protocol.

- Queue up to 10 files to upload or download for unattended
operation.

- Automatically send a "goodbye" command to hang up the phone
when the file transfer has completed

- Queue up to 5 numbers and dial in the background. IL will
prompt you when a connection is made.

- You can manually dial or choose from a 44 number dialing
directory.

- All commands in IL are invoked using simple one or two key
sequences.

- Dynamically alter communication parameters. You can change
communication speeds and choose between no parity and 8 data bits
or even parity and 7 data bits.

- Dynamically alter auto redial rate. You can vary the time between
redialing anywhere from 10 seconds to one minute.

In short, the Invisible Link is a powerful yet unobtrusive communications
program. It is both a timesaving utility and a productivity tool.

II. GETTING STARTED

2.1 What You Need (Basic Requirements)

The Invisible Link requires the following as a minimum:

- IBM PC, XT, AT, or 100% Compatible.

- DOS 2.0 or Later.

- IL requires about 26K of RAM when loaded.

- One Disk Drive or Hard Drive.

- Serial I/O Port with a Modem.

- CGA, EGA, IBM Monochrome, or Hercules Video Adapter.

- Any Monitor Capable of Displaying 80 Characters Per Line.

2.2 Loading Invisible Link

Loading The Invisible Link is a simple one step process. You pass IL
various configuration information via command line arguments. First, all
you need is the file IL.COM. There are no overlays to worry about.
Second, IL needs to know which communications port you will be using.
Third, IL also needs to know where IL.COM is stored. This is because when
you change your directory, IL needs to know where to update the directory.
By default, IL will assume that you will be using communications port 1
and that IL is stored on the current drive in the current subdirectory.

The format of the command line is as follows:

IL [COMM PORT] [FULL PATHNAME OF WHERE IL IS STORED]

Note that you can specify the pathname first and then the COMM port or
vice versa. The order does not matter.

EXAMPLES OF LOADING THE INVISIBLE LINK

A>IL means hit a carriage return. If you load IL this
way, COM1 will be used and IL will look for IL.COM on the current drive in
the current subdirectory.

A>IL 2 IL will use COM2 and update its directory on the current
drive in the current subdirectory.

A>IL 1 A:\IL.COM IL will use COM1 and update its directory on
drive A: in the root directory.

Note that when you are specifying a path that it must be a full path
including the three letter extension. For example, C:\IL\IL is not
valid but C:\IL\IL.COM is valid.

A>IL C:\IL\IL.COM 2 IL will use COM2 and update its directory on
drive C: in the subdirectory IL.

If IL is already loaded, you will get the "INVISIBLE LINK USING ALT-RIGHT
ALREADY LOADED -- ABORTING!" message. You will then return to DOS.

NOTE: It is strongly recommended that IL be loaded last in the chain of
memory resident programs. In particular, it must be loaded after CED in order
to properly enable the switches installed to prevent system crashes.

III. YOUR BASIC COMMANDS

3.1 Invoking Invisible Link

ALT - RIGHT-SHIFT => Invoke The Invisible Link. To invoke The Invisible
Link, simply hold down the and key simultaneously.
The Invisible Link was designed to be very robust so there are times when
IL will not let you "pop in" because it is not safe. Usually, it is not
safe when DOS is doing critical disk activity such as during a COPY or
TYPE command. Just wait until your disk drive light goes off and then hit
and key. When you "pop into" IL, you will be
presented with the following message, "TERMINAL MODE, HIT ALT - F10 FOR
HELP!". You are now ready to begin your communication session.

3.2 Terminal Commands

3.2.1 Setting Communication Parameters

ALT - P => Set Up Communication Parameters. Use this command when you
want to set the baud rate or choose the data, parity, and stop bits. The
Invisible Link supports the two most popular communication configurations:
even parity, 7 data bits, and 1 stop bit; and no parity, 8 data bits and 1
stop bit. When you hit ALT - P, will be presented with the following
prompt at the bottom of the screen.

Baud Rate For 8, 1, No Parity: 0) 300 1) 1200 2) 2400 3) 4800 4) 9600
Baud Rate For 7, 1, Even Parity 5) 300 6) 1200 7) 2400 8) 4800 9) 9600 |

At this point, type the number corresponding to the configuration you
wish. For example, hit 6 if you want 7 data bits, 1 stop bit, even
parity, and 1200 baud. An invalid entry will leave the configuration
unchanged. The user selected configuration will remain in effect until
you change it or if you reboot the computer.

3.2.2 Clearing The Screen

ALT - C => Clear The Screen. At any time you can clear the screen by
holding down and C key simultaneously.

3.2.3 Hanging Up The Phone

ALT - H => Hang Up The Phone. You may hang up the phone my hitting the
and H key simultaneously. After the phone is hung up, IL will
return you to terminal mode and prompt you with OK.

3.2.4 Auto-Redial Rate

ALT - R => Alter the Auto-Redial Rate. You will be prompted to enter a
number between 0 and 9 which causes the redialing rate to be adjusted
between 10 seconds and one minute, in 5 second intervals.

3.3 Making A Connection

3.3.1 Using The Dialing Directory

ALT - D => Access The Invisible Link Dialing Directory. Invisible Link's
dialing directory can be brought up by holding down the ALT and D key
simultaneously.

If the directory does not come up after hitting ALT-D, chances are your
modem may not be turned on. Try turning the modem on and restriking
ALT-D. The Invisible Link was designed to dial only if a modem is
connected.

3.3.1 Using The Dialing Directory

ALT - D => Access The Invisible Link Dialing Directory. Invisible
Link's dialing directory can be brought up by holding down the ALT
and D key simultaneously.

If the directory does not come up after hitting ALT-D, chances are
your modem may not be turned on. Try turning the modem on and
restriking ALT-D. The Invisible Link was designed to dial only if
a modem is connected.

3.3.1.1 Dialing A Number Or Queueing Numbers

After hitting ALT-D, IL will prompt you for the following: an
entry to dial, whether you wish to revise an entry, or whether
you wish to delete an entry. Type a number between 1 - 44 and IL
will acknowledge your valid entry by putting '>' by that entry.
You may queue up to 5 numbers. If you have less than 5 numbers
to dial, hit a empty and you will return to terminal
mode. At which point, IL will dial your numbers once every X
seconds (where X is the Auto Redial Rate) until a connection is made.
Furthermore, you may return to your application. When a connection
is made, IL will beep and inform you that a connection has been made.
Note, that hitting ALT-D again (or ALT-M) will stop any subsequent
dialing.

3.3.1.2 Adding New Entries Or Revising Existing Entries

By typing "R" at the above prompt, you may add new entries or
edit existing entries. A window will pop up and IL will prompt
you for an entry number. If the number you type has no existing
entry, then IL will bring up a blank entry. You may type in the
name and telephone number in the respective fields. For the baud
rate the following conventions are used:

Type 0 for 300 Baud Note that IL uses the data bits, stop
Type 1 for 1200 Baud bits, and parity from the last ALT-P
Type 2 for 2400 Baud command, but will use the baud rate
Type 4 for 4800 Baud specified in the directory for the
Type 9 for 9600 Baud given entry.

If the entry was an existing one, IL will display the old name,
telephone number, and baud rate. You may now input these
parameters. Note, if you hit a blank on the baud rate
field, IL assumes 1200 baud by default. After you have input all
the information for the directory, hit a blank and IL
will update the directory.

3.3.1.3 Deleting Entries

By typing "D", IL will prompt you for the number of the entry you
wish to delete. IL will then ask you "Are You Sure?". Typing
'Y' will delete the entry and 'N' will not delete the entry. To
return to the dialing menu, hit a blank

3.3.2 Manually Dialing A Number

ALT - M => Manually Dial A Number. You can manually queue up to 5 numbers
to dial. Hit Alt-M, and you will be prompted to input the telephone
numbers. Hit a blank when you are done. At this point, IL will
dial your numbers continuously in sequence until a connection is made. By
default, IL will wait 30 seconds between each redial, however, this rate
can be adjusted using ALT-R. If you want, you can now return to your
interrupted program and dial in the background. IL will beep when a
connection is made. Note, hitting ALT-M again while you are in terminal
mode will cancel the current dialing session independent of whether it was
started via ALT-D or ALT-M.

3.3.3 Terminating A Background Dial

ALT - LEFT-SHIFT => Terminate Background Dial. If you are not in terminal
mode (i.e. you are in your foreground application program), you can
terminate a background dial by holding down the ALT and LEFT-SHIFT
simultaneously. IL will acknowledge by beeping and displaying the
"BACKGROUND DIALING TERMINATED!" message.

3.4 Transmitting A File

3.4.1 Uploading A File

PAGE UP KEY => Start An Upload. To start an upload, hit the PAGE UP key
(it is located on the numeric keypad and is the number 9 on a standard IBM
PC). IL will prompt you for the name of the file you wish to upload. You
may specify full pathnames if your files reside in other directories other
than the current one (i.e. C:\IL\FOO.EXE is a valid path name). Next, IL
will prompt you for the command that will be sent to the host. For
example, U X FOO.EXE is a command that tells the host that you will be
uploading file FOO.EXE with XMODEM protocol. For an upload, IL will
automatically determine if CRC or Checksum protocol will be used. You
will then be prompted for a description of the file to be uploaded. This
will be transmitted to satisfy the request given by most current Bulletin
Board Systems. If desired, this request can be ignored by entering a
carriage return at the prompt. After entering the description, you will
again be prompted for another file to upload. With IL, you can queue up
to ten files to upload. That means you can enter ten files and ten upload
commands. If you will be uploading less than ten files, hit a blank
on the file prompt. IL will then ask you for a goodbye command.
This is a convenient way to hang up the phone after a transfer is
completed. Enter a "G" for goodbye. IL automatically sends a "Y' to
confirm that you want to hangup. At this point, the transfer will begin
in the background.

Note that once a transfer is going, you are returned to the foreground
program and locked out of the terminal. This means you can not hit ALT -
RIGHT-SHIFT to enter IL's terminal. Only after you see the "INVISIBLE
LINK TRANSFERS COMPLETED!" message and the bell rings is it safe to pop
into IL.

3.4.2 Downloading A File

PAGE DOWN KEY => Start An Download. To start a download, hit the PAGE
DOWN key (it is located on the numeric keypad and is the number 3 on a
standard IBM PC). First, IL will prompt you for the protocol that you
wish, CRC or Checksum. Select 1 for XMODEM-CHECKSUM or 2 for XMODEM-CRC.
CRC is less prone to errors in transmission but tends to slow the computer
down a little more than Checksum*. Next, IL will prompt you for the name
of the file you wish to download. You may specify full pathnames if your
files reside in other directories other than the current one (i.e.
C:\IL\FOO.EXE is a valid path name). Next, IL will prompt you for the
command that will be sent to the host. For example, D X FOO.EXE is a
command that tells the host that you want to download file FOO.EXE with
XMODEM protocol. After entering the download command, you will again be
prompted for another file to download.

If a file already exists, IL will prompt you if you wish to overwrite.
You may enter 'Y' if you wish to overwrite or 'N' if you do not. If after
5 seconds, you do not respond, IL will assume that you do want to
overwrite the file and the transfer will start. This feature was
incorporated into IL for the sole purpose of permitting unattended
transfers.

With IL, you can queue up to ten files to download. That means you can
enter ten files to download and ten download commands. If you will be
downloading less than ten files, hit a blank on the file prompt.
IL will then ask you for a goodbye command. This is a convenient way to
hang up the phone after a transfer is completed. Enter a "G" for goodbye.
IL automatically sends a "Y' to confirm that you want to hangup. At this
point, the transfer will begin in the background.

Note that once a transfer is going, you are returned to the foreground
program and locked out of the terminal. This means you can not hit ALT -
RIGHT-SHIFT to enter IL's terminal. Only after you see the "INVISIBLE
LINK TRANSFERS COMPLETED!" message and the bell rings is it safe to pop
into IL.

3.4.3 Invoking The Status Screen

ALT - LEFT-SHIFT => View File Transfer Status. At any time during a file
transfer, you can view the status of the current file being transferred by
hitting ALT - LEFT-SHIFT. You have access to the following information:
upload or download, full pathname of file, mode of transmission (CRC or
Checksum), Current Block Number, consecutive error count, and total error
count. If you are doing an upload, you will also see the total number of
blocks for that file. Once in the status screen, hitting 'Q' will abort
the transfer of the current file and proceed with the next file in the
queue. Hitting any other key will return you to the foreground program.
You can pop into the status screen as many times as you wish.

IL will abort the transfer itself after 10 consecutive errors and proceed
with the next file in the queue if there is one. Please note that your
total error count will be higher than when you are using a conventional
communications program. This is because IL is transferring in the
background. So, if you see a high total error count, don't be alarmed.
IL was designed with a robust error recovery system, so chances are the
file was sent properly.

3.5 Exiting Invisible Link

ALT - X => Exit The Invisible Link But Leave Online. You can exit IL by
hitting ALT-X. This will leave you online and return you to the suspended
foreground application program. You can enter and leave the terminal as
many times as you wish.

ALT - Q => Exit The Invisible Link And Hang Up The Phone. You can exit IL
and hang up the phone by hitting the ALT and Q key simultaneously. IL
will prompt you with "Are You Sure You Want To Disconnect?". Typing 'Y'
will hang up the phone and return you to your suspended foreground
application. Hitting any other key will return you to the terminal.

IV. SUMMARY OF COMMANDS

KEYSTROKE COMMAND

ALT - RIGHT-SHIFT ENTER INVISIBLE LINK.

ALT - X EXIT INVISIBLE LINK BUT LEAVE ONLINE.

ALT - Q EXIT AND HANG UP PHONE (DROP DTR).

ALT - P CHANGE COMMUNICATION PARAMETERS.

ALT - H HANG UP PHONE AND RETURN TO TERMINAL.

PG UP START AN UPLOAD.

PG DN START A DOWNLOAD.

ALT - D DIAL A NUMBER USING A DIRECTORY.

ALT - M MANUALLY DIAL A NUMBER.

ALT - R ALTER THE AUTO-REDIAL RATE.

ALT - LEFT-SHIFT TERMINATE BACKGROUND DIAL OR ENTER
FILE TRANSFER STATUS SCREEN.


V. TIPS ON USING THE INVISIBLE LINK

5.1 Getting The Most Out Of The Invisible Link

As with any memory resident program, contention may occur when running
with other memory resident programs. The only way to check compatibility
is to test IL with that particular memory resident program. IL has been
successfully tested with SIDEKICK(tm), SQZ(tm), CED(tm), and PRINT.COM to
name a few. It is quite a sight to see a background transfer going on
simultaneously with a background printing with no noticeable degradation
to the foreground application program. Note that with disk intensive
application programs such as DBASE(tm), you will probably notice more
degradation than if you were using LOTUS 1-2-3(tm).

Also, application programs that take over certain interrupts and are not
well behaved may interfere with the background transfer. The only way to
check compatibility is to try a background transfer or dial while using
that particular program. You will probably know right away if IL is
compatible with that program. IL has been extensively tested with DBASE
III+(tm), LOTUS 1-2-3(tm) (ALL VERSIONS), MICROSOFT(tm) COMPILERS AND
ASSEMBLER, TURBO PASCAL(tm), MANUSCRIPT(tm), AND NOVELL ADVANCED NETWARE
286(tm) VERSION 2.0.

VI. ERROR MESSAGES

INCORRECT DOS VERSION -- USE 2.0 OR ABOVE -- ABORTING! - IL requires DOS
2.0 or later.

IL.COM NOT FOUND, DIRECTORY NOT UPDATED! - When loading IL, you probably
did not specified the correct path (including extension) of where IL.COM
is stored.

TOO MANY ERRORS -- ABORTING! - IL has received 10 consecutive errors and
is aborting the transfer of the current file in the queue.

CANNOT OPEN FILE -- ABORTING! - IL could not open the file you wish to
transfer. Make sure you have specified a valid path.

COMM PORT OUTPUT ERROR -- ABORTING! - IL encountered a COMM port error.

ERROR WRITING FILE -- ABORTING! - IL encountered a error while writing the
transmitted file. This error usually occurs when you delete a file while
it is being transmitted.

ERROR READING FILE -- ABORTING! - IL encountered a error while reading the
transmitted file. This error usually occurs when you delete a file while
it is being transmitted.


** THE INVISIBLE LINK LICENSING AGREEMENT **

THE INVISIBLE LINK is being distributed in two separate versions. The
BULLETIN BOARD release version does NOT provide support for download
transfers. It is clearly identified by its lack of support of the PGDN
key in terminal mode. Pressing this key in terminal mode will display a
message providing information on how to obtain the fully supported version
of THE INVISIBLE LINK. The BULLETIN BOARD version is intended to give
users an appreciation of the capabilities of this powerful program. It
can be freely distributed and posted on any bulletin board system.

The fully supported release version of THE INVISIBLE LINK is copyrighted
material intended for use in unaltered form. Distribution of the release
version of THE INVISIBLE LINK in any form is a violation of copyright. The
program is provided "AS IS" without any warranty of any kind. Should the
program prove defective, the user shall assume the entire cost of all
necessary servicing, repair or correction. Site licensing of the release
version of THE INVISIBLE LINK is available by arrangement with Robert
Best. The release version of THE INVISIBLE LINK is intended for use on a
single machine. Making copies for use on other machines represents a
violation of this licensing agreement.

IMPORTANT NOTE: The BULLETIN BOARD release version of THE INVISIBLE LINK
does NOT provide support for download transfers. To obtain a fully
supported version of THE INVISIBLE LINK that includes full background
XMODEM download transfer capability, send check or money order payable to
ROBERT BEST in the amount of $35.00 (Calif. residents $37.10) to:

Robert Best
13681 Dall Lane
Santa Ana, CA 92705

The fully supported version of THE INVISIBLE LINK that includes background
download transfer capability is available solely by direct purchase from
Robert Best.

If any party is interested in purchasing the full source code to THE
INVISIBLE LINK, as well as the exclusive marketing rights to any
derivative thereof, please contact Robert Best at the above address to
discuss terms.


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