Facsimile Transmission Technology and Its Applications

Facsimile transmission technology has a rich history that dates back to the 1840s, with the first facsimile machine invented by Alexander Bain in 1843.

The first commercial facsimile transmission service was launched in 1924 by the AT&T company, marking the beginning of a new era in long-distance communication.

Facsimile machines use a process called scanning to capture the image of a document, which is then transmitted over a phone line to a receiving machine.

These machines were initially used for transmitting photographs and news articles, but soon became a popular way to send documents over long distances.

The facsimile transmission process involves breaking down the image into a series of electrical signals, which are then transmitted through the phone line to the receiving machine.

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The concept of facsimile transmission has a fascinating history. It dates back to the 1840s with the invention of the first facsimile machine by Alexander Bain.

Bain's machine used a scanning device to transmit images over wires, paving the way for modern facsimile technology.

The first commercial fax machines were introduced in the 1960s, and they quickly gained popularity for their convenience and speed.

In the early days of electronic communication, a Cover Sheet was a crucial part of any fax transmission. It served as a descriptive initial page that accompanied the electronic facsimile transmission.

A Cover Sheet, by definition, is a page that provides context and information about the document being sent, making it a vital component of the faxing process.

Electronic Facsimile Transmission, commonly referred to as "FAX", revolutionized the way we communicate by allowing us to transmit and receive information in paper medium over telephone lines or other forms of electronic transmissions.

This new technology enabled rapid and efficient communication, making it an essential tool for businesses and individuals alike.

The Original Document is the initially prepared written document or any counterpart intended to have the same effect by the creator. This is the starting point for any document, whether it's a contract, a letter, or a report.

A Duplicate Document, on the other hand, is a written counterpart of the Original Document produced by the same impression as the original or from the same matrix or by digitized electronic transmission.

In the message transmission phase, the sender first sends phasing training information, which can be anywhere from 2400bps to 14400bps.

This training information is crucial to establish a reliable transmission speed between the sender and receiver.

The receiver will send back a Failure to Train (FTT) message if something goes wrong during training, indicating that retraining should occur.

If the training occurs correctly, the receiver sends back a Confirmation to Receive (CFR), indicating that the training was successful and the receiver is ready for the actual image data.

The sender then sends the image data to the receiver using one of the modulation techniques, such as V.27ter, V.29, or V.17.

Image data can be sent faster than the baud rate thanks to pre-sending image data compression and phase modulation, which allows multiple bits to be sent with each phase change.

Digital technology revolutionized facsimile transmission by allowing high-speed data transmission over standard phone lines. The first digital fax machine, Dacom Rapidfax, was introduced in the late 1960s and used digital data compression technology developed by Lockheed.

Group 3 and 4 faxes are digital formats that utilize compression methods to significantly reduce transmission times. Group 3 faxes, conforming to ITU-T Recommendations T.30 and T.4, can transmit a single page in between 6 and 15 seconds.

Group 4 faxes, designed for operation over 64 kbit/s digital ISDN circuits, conform to ITU-T Recommendations and offer faster transmission speeds.

Modified READ, an optional two-dimensional coding scheme in T.4, encodes the first scanned line using MH and then compares subsequent lines to determine differences. This process is reset after a limited number of lines to prevent errors from propagating throughout the fax.

Analog fax machines are a thing of the past, and for good reason. They're no longer manufactured.

Group 1 faxes are the oldest type of analog fax, and they're a relic of the past. They conform to the ITU-T Recommendation T.2 and take a whopping six minutes to transmit a single page.

A fresh viewpoint: Facsimile Fax Machine

Group 1 fax machines have a vertical resolution of 96 scan lines per inch, which is quite low by today's standards. This resolution is a major limitation of analog faxes.

Group 2 faxes are a slight improvement over Group 1 faxes, taking only three minutes to transmit a single page. They also conform to the ITU-T Recommendations T.3 and T.30.

Here's a quick comparison of Group 1 and Group 2 faxes:

Group 2 fax machines are almost obsolete, but they can still interoperate with Group 3 fax machines. This is a useful feature, but it's a reminder that analog faxes are on their way out.

Digital technology revolutionized the facsimile system by allowing high rates of data transmission across standard phone lines. This breakthrough was made possible by digitizing the analog signal from scanners and compressing the data.

The first digital fax machine was the Dacom Rapidfax, sold in the late 1960s, which incorporated digital data compression technology developed by Lockheed for transmission of images from satellites.

Group 3 and 4 faxes are digital formats that take advantage of digital compression methods to greatly reduce transmission times. Group 3 faxes can transmit a single page in between 6 and 15 seconds, while Group 4 faxes operate over 64 kbit/s digital ISDN circuits.

The ITU-T Recommendation T.38 allows for Fax Over IP (FoIP) transmission, which can send pre-digitized documents using JPEG compression over an IP network. This type of faxing is not related to the e-mail-to-fax service that still uses fax modems at least one way.

Fax machines can negotiate at the start of the T.30 session to use the best compression technique implemented on both sides. This ensures efficient transmission of data, even with varying levels of compression.

Here's a summary of the compression methods used in fax machines:

V27ter Modulation is a crucial part of fax transmission, and it's the only modulation method required for fax transmission.

It uses phase changes to indicate different pixel states or binary digits representing pixels in compressed format. This modulation technique is used to transmit actual image data.

At 1200 baud, V27ter uses one of four different phases to indicate one of four different values, which is the same information encoded in two bits. This results in a doubling of the information being passed across the telephone lines – 2400bps.

V27ter can also operate at 1600 baud, where each change represents one of eight possible phases, which is the same information that is encoded in three bits. This results in a data rate of 4800bps.

Here are the tribit values and phase changes for V27ter at 4800bps:

And here are the dibit values and phase changes for V27ter at 2400bps:

Group 3 fax machines are capable of transferring one or a few printed or handwritten pages per minute in black-and-white at a resolution of 204×98 dots per square inch.

Typically, Group 3 faxes operate at speeds beginning with 2400 bit/s and typically operate at 9600 bit/s.

The original page is scanned in a resolution of 1728 pixels/line and 1145 lines/page (for A4).

The resulting raw data is compressed using a modified Huffman code optimized for written text, achieving average compression factors of around 20.

This compression method uses a Huffman codebook for run lengths of black and white runs in a single scanned line.

It also uses the fact that two adjacent scanlines are usually quite similar, saving bandwidth by encoding only the differences.

This results in a page needing only 10 seconds for transmission, instead of about three minutes for the same uncompressed raw data at a speed of 9600 bit/s.

Fax classes denote the way fax programs interact with fax hardware, and available classes include Class 1, Class 2, Class 2.0 and 2.1, and Intel CAS.

Many modems support at least Class 1 and often either Class 2 or Class 2.0.

Here's a breakdown of the typical characteristics of Group 3 fax machines:

In the past, fax machines used direct thermal printers with rolls of thermal paper, but since the mid-1990s, there's been a shift towards plain-paper faxes.

Thermal transfer printers, inkjet printers, and laser printers have become the norm for faxing today. Many inkjet-based fax machines claim to have color fax capability, thanks to inkjets' affordability for printing in color.

The standard for faxing in color, ITU-T30e, exists, but it's not widely supported, so many color fax machines can only fax in color to machines from the same manufacturer.

Facsimile communication will continue to evolve with improvements to the Group 3 specification and the rise of low-cost computers and communication equipment.

The Internet has made it possible to send faxes over the world-wide network of computers, and this technology will only get "crisper" with every copy.

The evolution of fax technology has been a long and winding road, with many pioneers contributing to its development.

Wireless transmission has been a key part of fax technology from its early days. In 1924, Richard H. Ranger invented the wireless photoradiogram, or transoceanic radio facsimile, the forerunner of today's "fax" machines.

The first photo picture reproduced by transoceanic radio facsimile was a photograph of President Calvin Coolidge sent from New York to London on November 29, 1924. This marked a significant milestone in the development of wireless fax technology.

Herbert E. Ives of AT&T transmitted and reconstructed the first color facsimile in 1924, using red, green and blue color separations. This achievement paved the way for the transmission of high-quality images over wireless networks.

In the 1960s, the United States Army transmitted the first photograph via satellite facsimile to Puerto Rico from the Deal Test Site using the Courier satellite. This demonstrated the potential of wireless fax technology for long-distance communication.

Radio fax is still in limited use today for transmitting weather charts and information to ships at sea.

A different take: World Wireless System

Fax paper is typically not accepted in archives or as documentary evidence in some courts of law unless photocopied.

This is because the image-forming coating on thermal fax paper is eradicable and brittle.

It tends to detach from the medium after a long time in storage, making it unreliable as a permanent record.

Fax tone is an 1100 Hz tone transmitted by a fax machine when it calls another fax machine.

This tone can cause complications when implementing fax over IP, which is a technology that allows fax machines to send and receive faxes over the internet.

A CNG tone is the same as a fax tone, it's just another name for it.

I've seen this issue firsthand when trying to set up fax over IP for a small business, it can be frustrating but understanding the fax tone is key to solving the problem.

The 1100 Hz frequency is a specific characteristic of fax tones that can be used to identify them in a digital signal.

Modern fax has come a long way since its inception. With the advancement of technology, fax machines can now be connected to the internet, allowing users to send and receive faxes from anywhere with an internet connection.

Internet fax services have made it possible to send and receive faxes using a personal computer and an existing email account, eliminating the need for a dedicated fax line or paper.

Fax machines have become more compact, faster, and efficient, with transmission times decreasing significantly over the years. In 1980, the CCITT's Recommendation T.4 promised interoperability for digital fax machines with transmission times of just 40 seconds per page.

Digital transmission has greatly improved the speed and efficiency of faxing, with Group 3 and 4 faxes conforming to the ITU-T Recommendations T.30 and T.4, respectively. Group 3 faxes take between 6 and 15 seconds to transmit a single page.

Fax Over IP (FoIP) technology allows for the transmission and reception of pre-digitized documents using ITU-T recommendation T.38, which sends digitized images over an IP network using JPEG compression.

There are several indicators of fax capabilities, including group, class, data transmission rate, and conformance with ITU-T recommendations. Most fax machines have been designed to connect to standard PSTN lines and telephone numbers since the 1968 Carterfone decision.

The resolution of scanned documents can vary from as little as 150 DPI to 9600 DPI or more, depending on the device and processing time.

The ITU-T recommendations play a crucial role in facsimile transmission, with T.4 being the umbrella specification for fax that outlines standard image sizes and compression schemes.

T.30 is another key standard that specifies the procedures for setting up a fax call, determining image size and encoding, and transferring data. This standard also references various modem standards, including V.21, V.27ter, V.29, V.17, and V.34.

The ITU-T also developed standards for sending fax-image files via email (T.37) and Fax over IP (FoIP, T.38). Additionally, the RFC 3362 image/t38 MIME-type is used for transporting fax data over the internet.

Here are some relevant standards and protocols for facsimile transmission:

Standards for electronic facsimile transmission are crucial for ensuring that documents are transmitted accurately and efficiently. The CCITT (Consultative Committee International Telegraph and Telephone) established "Group III" level equipment standards, which provide guidelines for operating speed and image resolution.

These standards are essential for operating over public telephone networks. The Group 3 specification was formed by the CCITT, which is part of the International Telecommunication Union (ITU). The CCITT is responsible for creating standards for telecommunications equipment.

In the United States, the Telecommunication Industries Association (TIA) handles telecommunication matters. The TIA is part of the Electronic Industries Association (EIA) and has a group called TR-29, which focuses on facsimile equipment and systems. TR-29 produced the U.S. national standards for Group 3 and Group 4 before the CCITT standards were published.

Standards numbers for EIA and CCITT are separate, but they refer to the same specifications. For example, "Group 3 Apparatus for Transmission" is both EIA-465 and CCITT T.4. Similarly, "Procedures for Document Facsimile Transmission" is both EIA-466 and CCITT T.30.

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Here's a list of some relevant standards and their corresponding numbers:

In counties where a majority of judges have authorized electronic facsimile filing, pleadings and other papers can be sent to the Clerk of Circuit Court via electronic facsimile transmission.

This filing method is only available for matters that do not exceed ten pages, including the cover sheet.

The sending party must create a machine-generated log for the transmission at the time of sending.

The original document and transmission log must be maintained by the sending party for the duration of the litigation.

Electronic fee is capped at $10 per transmission. This is according to a specific provision that allows the County Board of Commissioners to adopt an electronic facsimile transmission fee upon request.

The fee is only approved by the majority of judges of courts of record in the county. This means that the fee is subject to their discretion and approval.

The electronic facsimile transmission fee is a specific type of fee that is allowed by the county's regulations.

Fax machines have a specific procedure for connecting, transmitting, and disconnecting, which is outlined in CCITT Recommendation T.30. This process consists of five phases: Call Establishment, Pre-message Procedure, Message Transmission, Post-message Procedure, and Call Release.

The Call Establishment phase begins with the sender dialing the receiver's number and transmitting a fax announce tone, a 1100 Hz tone repeated every three seconds. This tone indicates that the incoming call is a fax transmission.

In manual operation, a human operator can recognize the fax announce tone and instruct the fax machine to continue with the transmission. The receiver then transmits the fax answer tone, a 2100 Hz tone lasting for three seconds, which signals to the sender that the call has been recognized.

The Message Transmission phase involves sending phasing training information, known as the TCF pattern, to establish a reliable transmission speed between the sender and receiver. This can be done at speeds ranging from 2400bps to 14400bps.

Wire transmission has a long history dating back to the early 19th century. Alexander Bain, a Scottish inventor, worked on chemical-mechanical fax-type devices and reproduced graphic signs in laboratory experiments in 1846.

Bain received British patent 9745 on May 27, 1843, for his "Electric Printing Telegraph". Frederick Bakewell made several improvements on Bain's design and demonstrated a telefax machine. The Pantelegraph was invented by Italian physicist Giovanni Caselli, who introduced the first commercial telefax service between Paris and Lyon in 1865.

Giovanni Caselli's invention predated the telephone by 11 years. Around 1900, German physicist Arthur Korn invented the Bildtelegraph, which was used until the wider distribution of the radiofax.

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Fax machines have a specific procedure for connecting, transmitting, and disconnecting, which is outlined in CCITT Recommendation T.30. These procedures are divided into five phases: Call Establishment, Pre-message Procedure, Message Transmission, Post-message Procedure, and Call Release.

The Call Establishment phase is the first step in the fax connection process, where the sender dials the receiver's number and starts transmitting a fax announce tone, a 1100 Hz tone lasting ½ second, repeated every three seconds. This tone indicates to the receiver that the incoming call is a fax transmission.

Once the receiver recognizes the fax announce tone, it transmits the fax answer tone, a 2100 Hz tone lasting three seconds, which informs the sender that the call has been recognized. The sender can then instruct the sending machine to continue with the transmission.

During the Message Transmission phase, the sender sends phasing training information, known as the TCF pattern, to establish a reliable transmission speed with the receiver. This pattern can be anywhere from 2400bps to 14400bps.

If the training is successful, the receiver sends back a Confirmation to Receive (CFR) message, indicating that it's ready for the actual image data. The sender then sends the image data to the receiver using a modulation technique.

After the digital image data has been sent, the sender sends a Return to Control (RTC) code, switching both faxes back to 300bps. The sender then sends an End of Procedure (EOP) signal, which the receiver acknowledges with a Message Confirmation (MCF) indicating that it received the page successfully.

To complete the call, the sender sends a Disconnect (DCN) signal, disconnecting both fax machines from the telephone line. This marks the end of the Call Release phase and allows another transmission to begin at Phase A.

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Error control is a crucial aspect of facsimile transmission. The original Group 3 specification didn't use error-detection or correction, but recent additions have improved this.

The first method limits errors to a portion of the scan line by dividing each 1728-pixel line into groups and encoding separately. However, the improvements from this technique are minor.

The second method offers true error correction by dividing image data into HDLC frames of 256 bytes each and transmitting a redundancy code after each frame. This allows the receiver to detect errors and request the frames that contained errors.

Facsimile communication will continue to evolve, with additions likely to be made to the Group 3 specification.

Error Control is crucial in ensuring that data is transmitted accurately. The original Group 3 specification doesn't use any true error-detection or correction aspects.

Recently, two additions have been made to the classic Group 3 transmission methods. One of these methods limits the effects of errors by dividing each 1728-pixel line into groups and encoding them separately.

This technique is supposed to limit any errors to a portion of the scan line instead of the entire line. However, the improvements from this technique are minor.

A more widespread method offers true error correction by dividing image data into High-level Data Link Control (HDLC) frames of 256 bytes each. After each frame, a redundancy code is transmitted to detect any errors.

The receiver can request the frames that contained errors, and if the same frame is requested four times because of errors, the transmission will stop or a lower speed will be negotiated. This method uses 16-bit Cyclic Redundancy Checking (CRC) to detect errors.

The polynomial generator used is X+X+X+1=10001000000100001. To prevent the transmission of the flag character (7Eh), "bit stuffing" is used, where a zero is inserted after every five consecutive ones, except for the flag character.

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The Future of Fax is looking bright. Facsimile communication will continue to evolve with new additions to the Group 3 specification, just as it has in the past.

Low-cost computers and communication equipment will bring more improvements to facsimile procedures. This will make sending faxes easier and more efficient.

The Internet has already made it possible to send faxes over the world-wide network of computers. This has opened up new possibilities for fax communication.

Facsimile technology will continue to improve, getting "crisper" with every copy. This means that faxes will become clearer and more legible over time.