Time Independent Escape Sequence
Encyclopedia
The Time Independent Escape Sequence, or TIES, was a short-lived modem
standard invented to avoid a patent held by Hayes Microcomputer Products
. TIES was an escape sequence
that switched the modem from "data mode" to "command mode", allowing instructions to be sent to the modem to control it.
available for use in the RS-232C port. He eventually settled on having two modes of operation, switching between them with an escape sequence
, +++. Of course, files being sent over the modem could contain the string +++. For instance, this page includes the sequence several times. If the modem simply looked for the string to arrive in the data, it would switch to command mode at inappropriate times. There needed to be some way to distinguish a deliberate command from random data.
Heatherington's solution to this problem was to introduce a delay on either side of the escape sequence, meaning that only a +++ would trigger the switch. A file containing the string being sent would not contain the pauses, so the modem would treat it as data to be sent, and stay in data mode. A user typing in the string deliberately would naturally pause after sending it to wait for the modem's response, inserting the pause without even being aware of it.
Hayes had initially filed for a patent on the electronic design of the Smartmodem in June 1981. In September 1983 they purchased a patent from Dr. Eaton of Bizcomp for $2 million, which included both a circuit design as well as a description of an escape sequence to trigger it. Hayes then updated the patent and re-filed it, this time including a lengthy abstract that focused entirely on the guard time and escape sequence, something that was mentioned only in passing in the original version. They received patent #4,549,302 in October 1985, Modem With Improved Escape Sequence With Guard Time Mechanism, commonly known as the "Hayes '302 patent" or the "Heatherington patent". It was this version that contained the description of the guard time.
A year after receiving the patent, Hayes decided to charge a $1 per modem license fee to use it. This included any modem already manufactured, and Hayes sent bills for millions of dollars to a number of major manufacturers. Lawsuits immediately started flying. Within a month of the license being made public U.S. Robotics
and Prometheus Products started a lawsuit against Hayes in an attempt to break the patent, followed immediately by Hayes suing both for infringement. Microcom
, Multi-Tech, and Ven-Tel then sued Hayes, and Hayes in turn sued Everex and Omnitel for patent infringement. Microcom and U.S. Robotics settled out of court and agreed to license the patent, but Everex, Ven-Tel, and Omnitel stuck it out in court where the Hayes patent was upheld.
TIES selected the string +++AT[some valid command]
, which was at that time an extremely large size – most hard drives of the era were about 40MB. Hayes estimated that a user transmitting files for one hour a day would encounter about six files per year that randomly contained this sequence and drop the modem into command mode. For the average user, this would be extremely mysterious.
Hayes had also licensed the '302 patent to two chipset manufacturers, Rockwell
and Silicon Integrated Systems
(SiS). In 1991 Rockwell introduced a new low-cost chipset supporting the new v.32bis 14,400 bit/s standard, one of the first to do so. It was an immediate bestseller, and other chipset companies immediately scrambled to catch up, all of them licensing '302 as well. Some even offered versions with both TIES and Hayes escape sequences, which could be determined via AT commands that returned the internal configuration of the modem, typically ATI4.
TIES was seen mostly in "off-brand" 1200 and 2400 bit/s modems, which were never a large market compared to the high-speed models that followed, it quickly disappeared in the early 1990s when almost all manufacturers switched to Rockwell chipsets, or one of its many clones. The one major exception was Telebit
, who used TIES in all of their models released after 1991, namely the T1600, T2500 and WorldBlazer. It is particularly interesting that Telebit would not licence the '302 patent, considering that they sold into an upscale market and generally cost over $1000.
Apparently for some time a number of Hayes employees would post to the UseNet
placing statements like "do you need a new modem? +++ATH" in their "sig". This would cause a TIES modem to hang up. If this is true, examples cannot easily be found in Google
's UseNet cache. Hayes apparently did include the string "+++ATH0" in their press releases, however. http://groups.google.com/group/comp.dcom.modems/browse_frm/thread/56bd9a5e5f2353a8 (Look at the top.) http://seclists.org/lists/bugtraq/1998/Sep/0193.html It was also used on IRC to disconnect people using dial up Internet access by sending ICMP
ECHO REQUEST containing the string +++ATH0 and thus the modem hanging up when the victims' computer sent back the ICMP
payload in the reply.
Note: The Hayes patent #4,549,302 expired on October 11, 2003.
Modem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...
standard invented to avoid a patent held by Hayes Microcomputer Products
Hayes Microcomputer Products
Hayes Microcomputer Products was a U.S.-based manufacturer of modems. They are particularly well known for their Smartmodem, which is introduced the ability to control the modem through commands sent in the data stream itself. The "smart modem" approach dramatically simplified operation, making...
. TIES was an escape sequence
Escape sequence
An escape sequence is a series of characters used to change the state of computers and their attached peripheral devices. These are also known as control sequences, reflecting their use in device control. Some control sequences are special characters that always have the same meaning...
that switched the modem from "data mode" to "command mode", allowing instructions to be sent to the modem to control it.
Hayes 302
When inventing the first Smartmodem, Dale Heatherington was faced with the problem of distinguishing commands from data given that there were only two serial pinsSerial port
In computing, a serial port is a serial communication physical interface through which information transfers in or out one bit at a time...
available for use in the RS-232C port. He eventually settled on having two modes of operation, switching between them with an escape sequence
Escape sequence
An escape sequence is a series of characters used to change the state of computers and their attached peripheral devices. These are also known as control sequences, reflecting their use in device control. Some control sequences are special characters that always have the same meaning...
, +++. Of course, files being sent over the modem could contain the string +++. For instance, this page includes the sequence several times. If the modem simply looked for the string to arrive in the data, it would switch to command mode at inappropriate times. There needed to be some way to distinguish a deliberate command from random data.
Heatherington's solution to this problem was to introduce a delay on either side of the escape sequence, meaning that only a
Hayes had initially filed for a patent on the electronic design of the Smartmodem in June 1981. In September 1983 they purchased a patent from Dr. Eaton of Bizcomp for $2 million, which included both a circuit design as well as a description of an escape sequence to trigger it. Hayes then updated the patent and re-filed it, this time including a lengthy abstract that focused entirely on the guard time and escape sequence, something that was mentioned only in passing in the original version. They received patent #4,549,302 in October 1985, Modem With Improved Escape Sequence With Guard Time Mechanism, commonly known as the "Hayes '302 patent" or the "Heatherington patent". It was this version that contained the description of the guard time.
A year after receiving the patent, Hayes decided to charge a $1 per modem license fee to use it. This included any modem already manufactured, and Hayes sent bills for millions of dollars to a number of major manufacturers. Lawsuits immediately started flying. Within a month of the license being made public U.S. Robotics
U.S. Robotics
USRobotics Corporation is a company that makes computer modems and related products. It sold high-speed modems in the 1980s, and had a reputation for high quality and compatibility. With the reduced usage of voiceband modems in North America in the early 21st century, USR is now one of the few...
and Prometheus Products started a lawsuit against Hayes in an attempt to break the patent, followed immediately by Hayes suing both for infringement. Microcom
Microcom
Microcom, Inc. was a major modem vendor during the 1980s, although they were never as popular as the "big three", Hayes, U.S. Robotics and Telebit. Nevertheless they hold an important place in modem history due to their introduction of the MNP error-correction and compression protocols, which were...
, Multi-Tech, and Ven-Tel then sued Hayes, and Hayes in turn sued Everex and Omnitel for patent infringement. Microcom and U.S. Robotics settled out of court and agreed to license the patent, but Everex, Ven-Tel, and Omnitel stuck it out in court where the Hayes patent was upheld.
TIES
For makers of low-cost modems, the $1 license fee represented a significant cost. A number of such manufacturers banded together to come up with a new system that avoided the patent, introducing TIES in 1991. Since the patent was based on the guard time concept, the new system had to be based solely on the string itself. Unfortunately, practically any string selected would eventually appear in a file, most obviously in a file describing the system.TIES selected the string +++AT[some valid command]
Gigabyte
The gigabyte is a multiple of the unit byte for digital information storage. The prefix giga means 109 in the International System of Units , therefore 1 gigabyte is...
, which was at that time an extremely large size – most hard drives of the era were about 40MB. Hayes estimated that a user transmitting files for one hour a day would encounter about six files per year that randomly contained this sequence and drop the modem into command mode. For the average user, this would be extremely mysterious.
Hayes had also licensed the '302 patent to two chipset manufacturers, Rockwell
Rockwell
- People :* Dick Rockwell, an American comic strip and comic book artist, nephew of Norman Rockwell* Francis W. Rockwell, a United States Congressman from Massachusetts* Francis W...
and Silicon Integrated Systems
Silicon Integrated Systems
Silicon Integrated Systems is a company that manufactures, among other things, motherboard chipsets. The company was founded in 1987 in Hsinchu Science Park, Taiwan.-Business:...
(SiS). In 1991 Rockwell introduced a new low-cost chipset supporting the new v.32bis 14,400 bit/s standard, one of the first to do so. It was an immediate bestseller, and other chipset companies immediately scrambled to catch up, all of them licensing '302 as well. Some even offered versions with both TIES and Hayes escape sequences, which could be determined via AT commands that returned the internal configuration of the modem, typically ATI4.
TIES was seen mostly in "off-brand" 1200 and 2400 bit/s modems, which were never a large market compared to the high-speed models that followed, it quickly disappeared in the early 1990s when almost all manufacturers switched to Rockwell chipsets, or one of its many clones. The one major exception was Telebit
Telebit
Telebit was a US-based modem manufacturer, most notable for their TrailBlazer series of high-speed modems. One of the first modems to routinely exceed 9600 bit/s speeds, the TrailBlazer used a proprietary modulation scheme that proved highly resilient to interference, earning the product an almost...
, who used TIES in all of their models released after 1991, namely the T1600, T2500 and WorldBlazer. It is particularly interesting that Telebit would not licence the '302 patent, considering that they sold into an upscale market and generally cost over $1000.
Apparently for some time a number of Hayes employees would post to the UseNet
Usenet
Usenet is a worldwide distributed Internet discussion system. It developed from the general purpose UUCP architecture of the same name.Duke University graduate students Tom Truscott and Jim Ellis conceived the idea in 1979 and it was established in 1980...
placing statements like "do you need a new modem? +++ATH" in their "sig". This would cause a TIES modem to hang up. If this is true, examples cannot easily be found in Google
Google
Google Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...
's UseNet cache. Hayes apparently did include the string "+++ATH0" in their press releases, however. http://groups.google.com/group/comp.dcom.modems/browse_frm/thread/56bd9a5e5f2353a8 (Look at the top.) http://seclists.org/lists/bugtraq/1998/Sep/0193.html It was also used on IRC to disconnect people using dial up Internet access by sending ICMP
Internet Control Message Protocol
The Internet Control Message Protocol is one of the core protocols of the Internet Protocol Suite. It is chiefly used by the operating systems of networked computers to send error messages indicating, for example, that a requested service is not available or that a host or router could not be...
ECHO REQUEST containing the string +++ATH0 and thus the modem hanging up when the victims' computer sent back the ICMP
Internet Control Message Protocol
The Internet Control Message Protocol is one of the core protocols of the Internet Protocol Suite. It is chiefly used by the operating systems of networked computers to send error messages indicating, for example, that a requested service is not available or that a host or router could not be...
payload in the reply.
Note: The Hayes patent #4,549,302 expired on October 11, 2003.