Telebit
Telebit was an American modem manufacturer, best known for its high-speed modems called TrailBlazer . The TrailBlazer, one of the first modems with a transmission speed of more than 9600 bit / s, used a proprietary modulation scheme that was extremely resistant to line interference. As a result, these products received an almost legendary reputation for their reliability on telephone lines with insufficient transmission properties. These modems were particularly popular in Unix installations in the 1980s and 1990s.
Telebit was originally founded by Paul Baran . Baran had previously founded a company called Packet Technologies in Cupertino , Silicon Valley , which worked on systems for interactive television. During this work he had the idea for a new kind of high speed modem and founded Telebit. Packet Technologies was an important test customer for Telebit in late 1985. Packet Technologies later failed; some employees were taken over by Telebit, while most of the others formed StrataCom , makers of the first Asynchronous Transfer Mode (ATM) switches .
PEP and the TrailBlazer modem
In contrast to the existing modems standardized by ITU-T with a maximum transmission speed of 2400 bit / s (V.22bis), the PEP ( Packet Ensemble Protocol ) method developed for the TrailBlazer used a large number (up to 512) Carrier frequencies closely spaced, each one modulated with 0, 2, 4 or 6 bits per baud . Under favorable conditions, this development could achieve transmission speeds of 18,031 bit / s; However, up to 20% of this must be deducted for internal modem communication. If a frequency range was distorted, had poor quality or was disturbed, it could be switched off; the data throughput was reduced with decreasing line quality, but was always possible. The PEP process has also been patented in Europe.
The TrailBlazer's high transfer rate was only available in one direction. At that time, modems were fairly simple developments; the transmission could be either full duplex or half duplex at the same speed. The TrailBlazer was the first "adaptable duplex modem". The modem worked half-duplex in the direction of the telecommunications line and duplex in the direction of the interface. The half-duplex switchover was based on the data in the transmit buffer and was not carried out for every character to be transmitted. Reversing the direction of a real half-duplex modem includes a waiting time of up to 100 ms to reduce line echoes. The TrailBlazer wanted to prevent this. To do this, the modem saved the data coming from the interface and only transferred it when the transmit memory was full.
- The partner modem is selected, data transfer is not started. The selection, the phase of the measurement of the line quality and then the constant switching of the transmission direction can be heard, since no data is pending transmission.
- In duplex mode, a continuous data stream is sent from both directions; the TrailBlazer saves the data and sends it out as a data block. Real-time operation is not possible, the delay between sending and receiving is more than one second. The data throughput in this measurement is approx. 800 characters / second for both directions. The audibly quieter part is data from the receiving direction.
- In simplex mode, a continuous data stream is only sent from one direction; the TrailBlazer saves the data and sends it out as a data block. Real-time operation is also not possible here, the delay between sending and receiving is more than one second. The data throughput in this measurement is over 1500 characters / second.
The Trailblazer was thus able to send large files quickly. However, this behavior made the interactive use of a simple terminal to a data center via a modem connection difficult. In such a connection, the sent character is often only displayed on the screen after a character echo has been received. This delay could last up to 1.5 seconds, due to the Trailblazer's attempt to prevent a reversal of direction on the transmission line. This also caused problems with some data transfer protocols, for example UUCP or Kermit . In these protocols, data transmission is only continued after a data block has been sent when an extremely short confirmation has been received, so the transmission direction must be constantly changed. This type of file transfer was sometimes slower than with conventional modems.
The TrailBlazer circumvented this problem through a special technique known as protocol spoofing . If the local computer sent a block of data to the modem for transmission, the modem answered immediately with a confirmation. This deception was possible because the TrailBlazer internally used a proprietary security protocol similar to the MNP process and the modem was thus secure that at some point a positive acknowledgment had to come from the remote end. This behavior is also used within the X.25 switching technology, since there is also a connection secured by HDLC between the switching systems (D-bit in the X.25 header, which is manipulated by the switching nodes).
In addition to the UUCP -g protocol, Kermit and the X-modem / Y-modem protocol, which is often used in asynchronous PC technology, were supported by means of protocol spoofing; the data throughput could be increased tenfold. There was support for the SDLC for synchronous data transmission .
- File transfer, X-modem protocol, no protocol spoofing activated. Data throughput approx. 145 characters / second. The constant switching of the transmission direction is audible; the acknowledgment of a data block with a length of 128 bytes consists of only one byte.
- File transfer, X-modem protocol, protocol spoofing enabled. Data throughput approx. 1400 characters / second. The receipts of the received side are not transmitted, the modem works almost in simplex mode.
This technology was not easy to implement; the TrailBlazer Plus, for example, used one of the first 32-bit microprocessors, the Motorola 68000 ; these modems have therefore generally been very expensive. Nonetheless, the TrailBlazer modems were very popular with Unix users, as their modulation type and protocol spoofing enabled them to achieve outstanding data throughput even with very poor communication links on which other modems could no longer work. The speed advantage over a standardized 2400 bit / s modem could be ten times as much. The cost of a long-distance connection to exchange UUCP emails quickly made the use of a TrailBlazer pay for.
The TrailBlazer was programmed using commands on the serial interface. While most simple commands on the AT command set of the company Hayes based, such as to dial a phone number or to terminate the connection, the special capabilities of the modem have been triggered by company-specific commands. Most of these commands simply wrote values in modem registers, which led to extremely long command lines that were almost incomprehensible without a manual.
In 1988 Telebit brought out the T1000 . This was a modem with a transmission speed reduced to 9600 bit / s in PEP mode. The modem was compatible with the existing TrailBlazers. The T2000 was an advanced TrailBlazer with the ability to transfer data synchronously; this was mainly used between central computers.
The NetBlazer
Another well-known product from Telebit was the NetBlazer , the world's first router that established a dial-up connection to the Internet when required .
The NetBlazer consisted of a small PC with the appropriate software in a large, modem-like case; together with a different number of modems or other connection options ( e.g. ISDN ) into the Internet. The users were connected and the NetBlazer was configured via a local data network using Ethernet .
The first version of the NetBlazer supported TCP / IP over the SLIP protocol, later PPP , IPX and AppleTalk were added. Later hardware versions replaced the Intel 80386 processor with a lower-cost microcontroller version of the Motorola 68030 , the MC68EN360.
Internationally standardized speeds and the TrailBlazer
The first TrailBlazer modems, T1000 and T2000 , were compatible with the internationally used V.22bis standard with 2400bit / s. This also enabled connections to modems from other manufacturers to be established.
The first international standard for dial-up modems in the telephone network with a speed of 9600 bit / s was published in 1984 as V.32 by the ITU-T . V.32 modems were initially very expensive, but Rockwell International released ready-made modem modules and chipsets that lowered prices. Telebit also expanded its T2000 with the Rockwell modem module and named it T2500 . In addition to PEP, this modem was also able to use 2400 and 9600 bit / s as the transmission speed. A version without PEP support was the T1500 . The T1600 , which came onto the market later , had the same functions as the T1500, but no longer used the Rockwell module, but an in-house development by Telebit with better performance data; this also made itself felt in reduced production costs. Both the T1500 and T1600 still cost more than $ 1,000; the top models from other modem manufacturers (such as Hayes and US Robotics ) were priced around $ 700.
The ITU-T standard V.32bis described in 1991 improved the transmission speed to up to 14,400 bit / s; many modem manufacturers quickly responded with improved or new modems. The Rockwell company developed an inexpensive V.32bis chipset; this enabled complete modems to be sold at prices below $ 300. The leading modem manufacturers, Hayes, USR, and Telebit, have had some difficulty entering a market now dominated by low-cost modems of equal or better quality than their own. Telebit began leaning toward modems with relatively mediocre V.32bis implementation while still trying to sell their products at a traditionally high price.
Telebit developed the T3000 modem, which only supported V.32bis; an update to PEP was planned. The WorldBlazer was launched in 1992; it cost $ 1,099. The modem was actually a T3000 with a further developed, 23,000 bit / s TurboPEP mode. The T3000 could be converted into a WorldBlazer. This hardware update consisted of two ROMs with the software and a PAL chip.
The PEP process works half-duplex on the line side. There have been various studies into a possible full-duplex PEP; to do this, echo suppression should have been developed as in Recommendation V.32. This technique was proposed to the ITU-T as a possible recommendation for a fast V. Modem standard. Recommendation V.34, a further development of the conventional V.32 technology, has been standardized. Due to the shrinking market for PEP modems, Telebit never implemented a full duplex version.
The Octocom Fusion and the FastBlazer V.34 modem
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The ITU-T decided to improve Recommendation V.32bis, and so it was clear in 1993 that the ratification process for the new 28,000 bit / s fast V.34 modem standard should be completed in 1994. Some modem manufacturers began producing new V.34 modems earlier. Some even brought models with their own intermediate standards , for example V.FC or V.32terbo , onto the market. These designations suggested a standardized version of the ITU-T to the modem buyer; in fact, only modems from the same manufacturer could establish a high-speed connection with one another.
Telebit also began to develop its own V.34 modem, but this took time. The company's management felt it was important to get such a product to market faster. As a result, she looked for other modem companies to manufacture and develop, and in January 1993 it was finally announced that Telebit was buying Octocom Systems , a small private modem company from Massachusetts. Octocom was developing a V.34 modem that should be ready for delivery quickly. All of Telebit's own activities in the modem area have been discontinued. The development of the NetBlazer continued until 1995 at Telebit's California headquarters.
The Telebit FastBlazer 8840 V.34 modem was presented in May 1994 in what could be called a model example of a false launch. When the FastBlazer was first introduced, it did not yet support the required V.34 technology, on the grounds that the standard had not yet been adopted. Although this was true for a month (V.34 was ratified in June), the FastBlazer was not shipped with an intermediate version of V.34. Other modem manufacturers had non-standardized previous versions on offer, for example the widespread fast V.FC. Telebit did not give an exact date for complete V.34 support, the statements were "in two or three months".
The situation worsened due to the fact that the FastBlazer also lacked fax support. Telebit announced that the company was working on an upgrade to be installed later. The FastBlazer also didn't support PEP, which Telebit viewed as a minor nuisance; but this was one of the few reasons why these modems were bought earlier. A PEP upgrade was useless for data connections with Telebit modems on only one side; without this technology, every other V.34 modem was a competitor.
The FastBlazer had an original introductory price of $ 1,399, while V.32bis fax modems were $ 200 or less, and professional V.34 modems were available for under $ 500.
It took seven months until Telebit finally supported the complete V.34 recommendation in January 1995. At the same time, a simple $ 399 modem, the TeleBlazer , was produced. At that time, Telebit had already lost many supporters. Even long-term proponents were negative on Usenet public forums; the medium that once made a major contribution to the spread of the TrailBlazer.
The end of the company
The Telebit company ran into major financial difficulties within a very short period of time that no longer seemed to be settable. At the end of 1993 she completed the merger with Octocom, with the idea of using the existing capacities there for the production of the NetBlazer at their headquarters in Chelmsford (Massachusetts, USA). The engineers at the company's headquarters in Silicon Valley quit; so it finally came to the closure of this plant on the west coast of the USA.
By the time this became known, the manufacturing costs at Octocom were already higher than on the west coast. The company was no longer able to repay loans to its creditors. New loans from various donors quickly became necessary, but this resulted in even higher costs. That only made things worse, and in December 1995 it was announced that the company was up for sale.
Telebit was bought by Cisco Systems in 1996 for $ 200 million ; the main reason was Telebit's experience with transmission technology on T1 lines, the primary rate connection common in the USA . Cisco wasn't interested in analog modems; the former management of Telebit took over this part of the business with the support of Cisco and founded Telebit Incorporated .
In the summer of 1997 Telebit Incorporated merged with ITK Telekommunikation ; the resulting company was bought by Digi International in July 1998 . Digi International was not interested in the now hopelessly outdated modem technology and immediately stopped production; the remaining inventory was sold in March 1999.
Further development of PEP modulation
The modulation method Orthogonal Frequency Division Multiplex (OFDM) , which is used today, among other things, in ADSL technology and wireless LAN , has its beginnings in the Packet Ensemble Protocol from Telebit. These methods also use the simultaneous FDM modulation of different subcarriers.
The trail blazer in Germany
The main board of the TrailBlazer was developed by Telebit. Distribution partners were responsible for adapting the lines to the national telephone networks; in Germany this was initially Kabelmetall electro GmbH (ke) . The Trailblazers were sold by ke under their brand name Logem . The Deutsche Bundespost , later Deutsche Bundespost Telekom, sold or rented the devices under the name MDG (MoDemGerät) or MDB (MoDemBaugruppe) , the WorldBlazer was available as a module version for rack mounting as MDB 23MX-21. The first of these modems, the MDG 19K-31, had only one approval and one basic setting for ITU-T recommendation V.22bis; however, the switch to PEP mode is described on the first page of the manual. These modems cost around 5000 DM in Germany.
Well-known modems from Telebit
| model | year | Remarks | German name introduction |
|---|---|---|---|
| Trailblazer | 1985 | Original model, transmission speed approximately 18,000 bit / s | |
| Trailblazer + | ? | improved model, over 19,000 bit / s | |
| T1000 | 1988 | Simple model with a PEP variant of a maximum of 9,600 bit / s | |
| T2000 | ? | Synchronous data transfer possible | MDG 19K2-31 October 1989 |
| T2500 | ? | T2000 with the V.32 module (9,600 bit / s) from Rockwell | MDG 19K2-21 August 1990 |
| T1500 | ? | No PEP, V.32 module from Rockwell | |
| T1600 | ? | V.32, Telebit's own development | |
| T3000 | ? | V.32bis modem (14,400 bit / s) with fax support | |
| WorldBlazer | 1992 | T3000 with TurboPEP (over 26,000 bit / s) and later also fax support | MDG 32MX-21 August 1992 |
| FastBlazer | 1994 | V.34 modem with 28,800 bit / s | |
| TeleBlazer | 1995 | Simple model of a V.34 modem | |
| QBlazer | ? | V.32 modem powered by batteries | |
| QBlazer + | ? | V.32bis modem powered by batteries | |
| NetBlazer | ? | Ethernet router with access to the Internet via SLIP or and PPP |
Web links
Brief overview of the history of Telebit (English)
Individual evidence
- ↑ Image of a TrailBlazer +
- ↑ ITU-T Recommendation V.22 bis: 2400 bits per second duplex modem using the frequency division technique standardized for use on the general switched telephone network and on point-to-point 2-wire leased telephone-type circuits
- ↑ A Brief Technical Overview of the Telebit Trailblazer Modem .
- ↑ Software patent: Packetized ensemble modem ( Memento of the original dated December 2, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
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↑ Measurements of the data throughput on the MDG 19K2-31 modem, no data compression, PEP mode; Test text Fox (English) according to ITU-T R.52, measurement time 30 minutes:
- Duplex operation: send direction 8,006 bit / s, receive direction 8,016 bit / s
- Simplex operation: 15,418 bit / s
- ↑ UUCP-g with Telebit support
-
↑ Measurements of the transmission time of a file with the MDG 19K2-31 modem using the X-Modem protocol, no data compression, PEP mode, file length 1,047,777 bytes. The transferred file was a non- compressible zip archive.
- Without protocol spoofing: 119 minutes
- With protocol spoofing: 12 minutes
- ↑ Example configurations, mainly by changing individual registers such as Sxx = yyy
- ↑ Announcement of the T1000 with reduced performance features
- ↑ Picture of a NetBlazer ( Memento from August 28, 2008 in the Internet Archive )
- ↑ Press release 1996 from Telebit with mention of NetBlazer ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ↑ ITU-T Recommendation V.32: A family of 2-wire, duplex modems operating at data signaling rates of up to 9600 bit / s for use on the general switched telephone network and on leased telephone-type circuits
- ↑ ITU-T Recommendation V.32 bis: A duplex modem operating at data signaling rates of up to 14 400 bit / s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits
- ↑ Collaboration of Telebit in the CCITT (today ITU-T)
- ↑ ITU-T Recommendation V.34: A modem operating at data signaling rates of up to 33 600 bit / s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits
- ↑ The New York Times: Cisco Systems Approves Acquisition of Telebit
- ↑ Purchase of the company by its own management ( Memento from December 17, 2004 in the Internet Archive )
- ↑ Purchase of the company by its own management, further information
- ↑ Telebit and ITK announce intention to merge in third quarter of 1997 ( Memento from July 8, 2012 in the web archive archive.today )
- ↑ Price of the TrailBlazer in Germany
- ↑ Data services ISDN, MDG 19K2-31, operating instructions, post, copyright 1989 kabelmetal electro GmbH, technical status 10/89, publisher kabelmetal electro GmbH, product area data transmission technology
- ↑ Dateldienste, MDG19K2-21, operating instructions, Telekom Deutsche Bundespost, KNr. 665 537 400-0, as of 08/90
- ↑ Teledat MDG23MX-21, operating instructions, Telekom, K-No. 665 537 107-8 as of August 1992
