Telebit
From Free net encyclopedia
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 bps speeds, the TrailBlazer used a proprietary modulation scheme that proved highly resilient to interference, earning the product an almost legendary reputation for reliability despite mediocre (or worse) line quality. They were particularily common in Unix installations in the 1980s and 90s.
Telebit was originally founded by Paul Baran, one of the inventors of the packet switching networking concept. Baran had recently started a networking company known as Packet Technologies on Bubb Avenue in Cupertino, California, which was working on systems for interactive television. While working there, he hit on the idea for a new way to implement high-speed modems, and started Telebit across the street. Packet Technologies was a major beta customer for Telebit in late 1985. Packet Technologies later failed, and several of their employees were folded into Telebit, while most of the others formed StrataCom, makers of the first Asynchronous Transfer Mode (ATM) switches.
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PEP and the TrailBlazer
In contrast to then-existing ITU V-series protocols, notably the common 2400 bit/s V.22bis, the TrailBlazers' proprietary PEP (Packet Ensemble Protocol) modulation employed a large number (initially up to 512) of closely spaced carrier frequencies, each modulated at a leisurely 6 baud, encoding 0, 2, 4 or 6 bits per interval. Under favorable conditions, the devices could reach data rates of 6 baud x 6 bits-per-baud x 512 carriers = 18432 bits per second. If a particular carrier was distorted, attenuated or interfered with, it could be turned off, allowing the data rate to degrade gracefully with decreasing line quality.
The Trailblazer's high data rate mode was available in one direction only. While often labelled "half duplex", the modem did have a low-speed return channel which was used to control the transfers to give the impression of full duplex operation. Both modems included large buffers that accepted data from their host computer and attempted to send it as quickly as possible; using the backchannel, the two modems exchanged how much data was waiting in the local buffer on either end, and would switch which end had the high-speed side of the connection when its buffers became too full.
The low-speed channel was adequate for many file transfer protocols of the day, but seriously slowed UUCP transfers, which sent far too many acknowledgement (ACK) messages and required more bandwidth than was available. To address this important application, the Trailblazer had the ability to spoof the UUCP "g" protocol – it would simulate the remote host's ACK responses locally in the modem, allowing the sending machine to move onto the next packet immediately without waiting for a reply. The error correction normally being applied was instead handled using a proprietary replacement protocol operating on top of the the MNP error-correcting protocols to talk to the remote modem. In general, spoofing worked well with any protocol that used small packets, and thus generated lots of ACK messages; support for XModem and Kermit followed.
Support for these features did not come easily; the TrailBlazer Plus, for instance, used a Motorola 68000 to drive its electronics. This meant that the TrailBlazers were generally very expensive. However, its spoofing ability made the TrailBlazer modems extremely popular in the Unix world, as it could dramatically improve UUCP throughput, even at low connection speeds on very noisy lines. Improvements of over 10 times over a 2400 bps modem were not uncommon. Sites that required long-distance telephone calls to exchange UUCP mail could pay for the price of a TrailBlazer in long-distance savings fairly quickly.
The Trailblazers also introduced an extensive set of commands for setting up its various options. While most of the simple commands were based on the Hayes command set, like dialing a number or hanging up a phone, their proprietary capabilities were supported by proprietary commands and syntax. Most of these took the form of register=value pairs, leading to extremely long and almost undecipherable setup strings.
In 1988 Telebit added the T1000, essentially a TrailBlazer limited to a lower-speed 9600 bit/s version of PEP, remaining compatible at that speed with existing TrailBlazers. The T2000 added support for four-line synchronous communications, typically used with leased lines between major computer installations.
The NetBlazer
Another of Telebit's famous products was the world's first on-demand internet dialup router, the NetBlazer. The product was developed by a team led by Mike Ballard, formerly of Packet, who eventually became Telebit's CEO in 1986, and president in 1992.
The NetBlazer essentially consisted of a small-form-factor PC combined with custom software and one of a variety of modems or other connection systems (ISDN, etc.) combined into a large modem-like box. Users connected to it via ethernet, which was also used for maintenance commands and setup.
In it's first release the NetBlazer's supported TCP/IP using SLIP, but a later upgrade added PPP as well as support for IPX and AppleTalk. Later versions of the hardware switched from the Intel 80386 to a low-cost microcontroller version of the Motorola 68030, the MC68EN360.
Increasing speeds
The original TrailBlazers, T1000's and T2000s were backwards-compatible with the 2400 bit/s v.22bis standard, allowing them to connect with what was then the most common modem speed when talking to other brands of modems. Starting with the widespread use of v.32bis around 1991, Telebit increasingly slipped in terms of relative performance, while still trying to sell their products at their traditional high price points.
Their first move into this market was the T1500, which supported v.32 via a Rockwell chip-set that ran "beside" an otherwise standard T1000. The T1600 was similar, but used a v.32 implementation written by Telebit that ran on the already-existing processor that drove PEP, thereby lowering production costs. Both were listed at over $1000, although at the time a "1st tier" product from Hayes or US Robotics generally cost about $700.
In 1991 Rockwell introduced a chipset supporting the new 14,400 bit/s v.32bis standard, which was first popularized in the famed SupraFAXModem 14400. Telebit didn't respond for some time, finally doing so with the T3000 with lacked PEP support. Telebit had originally claimed they would offer a PEP upgrade for the T3000, but apparently later dropped these plans. There may have been some incompatibility between the original PEP negotiation tones and v.32bis, but it is not entirely clear if this was the reason. Thus the T3000 had all the cost and none of the features of the earlier Telebit modems, and was not very popular as a result.
Telebit finally addressed these issues in the $1,099 WorldBlazer model, introduced in early 1994. The WorldBlazer was essentially a T3000 with the new 23,000 bps TurboPEP mode. The company offered replacement hardware to many of those customers who had expected PEP in the T3000, which went some way to smooth over any bad feelings.
The FastBlazer Debacle
The CCITT moved quickly to improve on v.32bis, and by 1993 it was clear that the ratification process for their new 28,800 bit/s v.34 standard was going to be finalized in 1994. Companies lined up to start production of new v.34 designs, some going so far to introduce models based on interim standards, notably v.FC.
Telebit responded to v.34 with the introduction of the FastBlazer in May 1994, in a release that is a textbook example of product mismanagement. When the FastBlazer was first introduced it did not include v.34 support, with management stating that they couldn't do so because the standard was not yet ratified. Although this was true (for one month anyway, it was ratified in June), the FastBlazer did not ship with an interim standard either; even AT&T's largely-ignored v.32terbo would only be available as an upgrade in July, there were no plans to support the widespread v.FC at all, and no date was set for full v.34 support other than "two or three months".
Making matters worse, the FastBlazer didn't include either PEP or fax support, and while Telebit stated that an upgrade to add these features would be available, they would be charging for it. All this for an introductory price of $1,399, when v.32bis faxmodems were available for $200 or less, and industrial-quality v.34 designs were soon available for under $500.
It took a long seven months before Telebit finally introduced v.34 support in January 1995, also releasing the $399 TeleBlazer "low-end" model at the same time. By this point any goodwill the company had was lost, and even long-time supporters were publically pooh-poohing the company on the UseNet, the medium that originally drove the widespread adoption of the TrailBlazer.
End of the company
The company quickly found itself in serious financial difficulty, which they were never able to address. Late in 1994 they merged with Octocom Systems, a small modem company in Chelmsford, Massachusetts. The idea was to use Octocom's manufacturing capability, downsizing the existing Cupertino office to become a NetBlazer development site. The head of NetBlazer development quit in the spring, and the west-coast office was then closed.
As it turned out, the manufacturing costs at Octocom were actually higher than their original west-coast factory, and soon they were unable to pay bills on time with their major component supplier. New lines of credit were quickly arranged with various distributers, but this resulted in higher parts costs. This simply made matters worse, and by December 1995 it was publically known that the company was up for sale.
In 1996 the bulk of their networking business was acquired by Cisco Systems for $200M, primarily for their ISDN modems and NetBlazer systems. The original modem side of business was spun off to the existing management team to become Telebit Incorporated. In the summer of 1997 they merged with another small company, ITK Telekommunikation, which was purchased a year later in July 1998 by Digi International, makers of the DidBoard multi-port serial card for PCs. Digi was uninterested in the modem line, which was now hopelessly outdated, and immediately cancelled production. Remaining inventory was liquidated in March 1999.
While the Trailblazers have generally been displaced by modems implementing the higher-rate V.34/V.90 series standards, and although they have been out of production since the mid-1990s, many TrailBlazers continue to be in operation to this date, and repair services are still available.
Models
| Model | Year | Capabilities |
| Trailblazer | 1985 | Original model, "19000" bps |
| T1000 | 1988 | lower-cost model limited to 9600 bit/s |
| T2000 | ? | synchronous link support |
| T1500 | ? | V.32 (9600 bit/s) support added based on Rockwell module |
| T1600 | ? | V.32 support, Telebit-internal implementation |
| T2500 | ? | V.32 support and PEP |
| T3000 | ? | V.32bis(14400 bit/s) and fax support |
| WorldBlazer | ? | T3000 with PEP and, later, fax |
| FastBlazer | ? | V.34 (28800 bit/s) |
| NetBlazer | ? | ethernet-connected on-demand SLIP and PPP router |
Legacy
Orthogonal frequency-division multiplexing (OFDM), which is used in both the ITU Asymmetric Digital Subscriber Line (ADSL) and IEEE 802.11 Wireless LAN standards, has some of its roots in the Packet Ensemble Protocol. Notably, these protocol's reused PEP's concept of carrying a single data-link over many lower rate FDM sub-carriers.