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Micros and LSI Chips Are Fueling the Latest in Modem-Mux Advances.

Modems are getting faster, smaller and smarter, thanks to advances with microprocessors and large-scale integrated (LSI) circuits. LSI chip sets have given modems capabilities that were technically impractical or too expensive to consider including in the past; microprocessors have added "intelligence", manifested in such features as auto-equalization and network diagnostics.

As Hank Morgan, transmission product manager with Gandalf Data, points out, modems are no longer operating only on the lowest level of the ISO reference model, the physical level. "Modems with error correction, for example, are operating on the frame level, which has as a basic function the provision of error-free channels," Morgan notes. Likewise, modems that provide auto-dial capability extend into the transport level. "At the rate modem technology is developing, operation at additional levels may soon be included", he concludes.

Even though modems can do more, the main concern of most users is speed. In this regard, many modem vendors have truly distinguished themselves. Using Trellis codinG, modems can now operate reliably over voice-grade lines at speeds of 14.4, 16.8 and even 19.2 kb/s. These high-speed modems also come with intergral multiplexers, giving users unprecedented flexibility in mixing data rates over a single line and, through statistical multiplexing, increasing aggregate data rates even further. Similar advances have been made with specialized modems, such as local-data sets, data-over-voice modems, and models designed for media other than copper wire, such as fiber-optic links.

Speed is also a motivating factor with multiplexers suppliers, many of whom have added T1 models to their product line to take advantage of the increased availability of 1.54-Mb/s service. Increasingly, T1 multiplexers are being used in networks rather than point-to-point applications, giving rise to software-driven units, switching features and network-management capabilities.

Also, a growing number of statistical multiplexers now perform polling operations and integrate such features as switching, alternate routing and contention for host ports.

What follows is a rundown on recent developments with both modems and multiplexers:

AT&T Information Systems' family of Dataphone II products includes a 9.6-kb/s modem that offers multiplexing capabilities and advanced diagnostics. With the 2096A, users can run tests without shutting down the system, since the modem can test a Level 1 diagnostics permit continuous polling from a central-site modem of all tributary modems in accordance with a polling list entered by the user.

In addition, the control modem may periodically poll a special address to determine if any tributary has requested a maintenance test. If so, the control modem runs the test. Adding a diagnostic console provides expanded test and command capabilities and allows users to extend the duration of certain tests and to monitor and test any modem in the network.

A still-higher level of diagnostic sophistication can be achieved through the addition of the network controller that provides a command to local or remote units from a single point. The companion 2096C modem features a 30-millisecond training time and can operate in a multipoint environment with up to 15 tributaries. The modem also incorporates diagnostics for use on all three levels of Dataphone II service.

Another Dataphone II modem, the 2212C, builds on the 212 technology with such additional features as multiple speedS, automatic dialing and answering capabilities, call-progress monitoring, and keyboard control of all functions. The companion 2212D is a reduced-cost alternative for the 212A in a central-site, multiple-modem arrangement. Likewise, the 2024T is a low-cost version of the 2024A for remote Dataphone II network sites.

As for data service units, the 2600 Series combines all the features of the 2500 Series, with connection to Dataphone II diagnostic control devices and multipoint addressability. The 2500 Series DSU, which combines the capabilities of the channel service unit and the data service unit into a compact device, may be upgraded to the 2600 Series with the addition of a diagnostic module without requiring additional space.

Amdahl's Communications Systems Division recently introduced a family of modems designed "with nontechnical operators in mind," and a series of statistical multiplexers with channel-switching and port-contention features. The 1000 Series modems operate at data rates from 1.2 to 14.4 kb/s and employ light-emitting diodes and liquid-crystal displays to help nontechnical operators run diagnostics. The modems incorporate an integral test-pattern generator, built-in eye-pattern generator and bit-error-rate detector, and provide multiport capability with a built-in multiplexer. Trellis coding is used to cancel noise errors and the modems provide a fast poll of 7.5 ms.

The 2500 Series statistical multiplexers permit up to 16 remote devices operating at channel rates of up to 9.6 kb/s to be concentrated on a link or trunk operating at rates to 64 kb/s. Network management capabilities provide individual channel monitoring and diagnostics, including status, statistics and loopback, and also provide link or trunk monitoring and diagnostics, including utilization, number of transmit and received retransmissions, EIA signal status and loopback. Network control can be exercised from either a local or remote location, using either a front-panel touchkey pad and an alphanumeric display, or an asynchronous terminal connected to the executive port on the multiplexer.

Anderson Jacobson has strengthened its modem line with new models operating at speeds from 2.4 to 14.4 kb/s. The AJ 1411 modem uses Trellis coding and a built-in multiplexer to support six channels on a single unconditioned line at a combined data rate to 14.4 kb/s. Port speeds for local and remote modems can be controlled from a central site using front-panel controls and a liquid-crystal display. Local and remote diagnostic features provide continuous monitoring of selected port interfaces and overall network testing. An integral test-pattern generator and bit-error-rate detector permit network

performance tests without external equipment or remote operators. When line quality falls, the modem can operate at fallback rates of 9.6, 7.i or 4.8 kb/s.

With the latest addition to its 9.6-kb/s modem line, the San Jose, California, firm combines a CCITT V.29-compatible modem with a four-channel time-division multiplexer for point-to-point applications. The AJ 9611 provides front-panel programming, a liquid-crystal status display and a powerful automatic adaptive equalizer. All switch settings and speed changes can be downline loaded without remote operator intervention. The modem also has an integral test-pattern generator and bit-error-rate detector.

At lower speeds, the CCITT V.27bis/ter-compatible AJ 4801 handles point-to-point and multipoint applications at rates of 2.j or 4.8 kb/s, while the AJ Data Modem/2400 provides Bell 212-compatible operation at 1.2 kb/s and CCITT V.22 compatibility at 2.4 kb/s.

The AJ 48901 sells for $1,495. It employs digital signal processing and advanced diagnostics, including error detection and six different loop tests that can be operated centrally. All remote strap settings and speed changes can be downline loaded to remote sites centrally without remote operator intervention. Front-panel switches and a liquid-crystal display simplify programming and monitoring.

the Data Modem/2400 is priced at $795. It stores up to 20 log-on sequences, each of which can be linked with one or more of the 20 telephone numbers stored in the modem.

Case Communications has added Trellis-encoded forward error correction to its Case 4096 modem, reportedly making it the first multipoint 9.6-kb/s modem to feature the error detection and correction scheme. Trellis-coded modulation is already featured in teh 14.4-kb/s Case 4144 in compliance with the CCITT V.33 standard. The algorithm used to encode the data stream enables the receiving modem not only to detect errors but to reconstruct the correct signal.

A Case-patented pre-distortion equalizer gives furtehr protection against line distortion and consequent errors. The transmitting modem sends a test signal down the line prior to the data stream to detect the level of distortion imposed. The transmission signal is then adjusted to overcome the predicted distortion.

The modems are supported by the Case Series 5000 network-management system and are available with diagnostic and multiplexer cards. The diagnostic card monitors the state of the modem, the performance of the line, and the interface between the terminal and the modem, reporting the results back to the Series 5000 network-management processor over a secondary channel. If a line deteriorates, a series of alarms is triggered by the card, which monitors against pre-assigned parameters. The multiplexer option allows users to split the available bandwidth in a variety of ways for maximum flexibility. Every port on the multiplexer is equipped with RS-232 interface control signals, allowing remote modems to dial in to an individual port.

The latest addition to the Series 4000 diagnostic modems, the Case 4024, operates in either point-to-point or multipoint environments at 2.4 kb/s. It comes with a 145-character front-panel display and touch-sensitive front-panel pad for simplicity of use, as well as a battery-protected memory.

Multiplexing Unit for PBX Plugs into Phone Jack

For PBX users, the Silver Spring, Maryland, firm has introduced a multiplexing unit that allows terminals to communicate through existing telephone circuit wiring with any number of local and remote terminals and computer resources. Installing the compact Grapevine access unit simply involves plugging the unit into a telephone jack. The telephone terminal plugs into the access unit. Moving terminals then becomes a simple matter of unplugging the access unit from one telephone jack and plugging into another at the new location.

Voice and data from the Grapevine access unit travel to the main distribution frame of the PBX and then to a Grapevine distribution unit, where the voice and data are separated and the voice returned to the PBX to be handled in the normal manner. Data may be routed to a local host computer or to a Case DCX network.

Codex continues its tradition as a pioneer of high-speed modems with the announcement of its 2680model, reportedly the first 19.2-kb/s modem to deliver 99.9-percent error-free data transmission over better than 98 percent of D1-conditioned lines. The unit is also the first modem to use 64-state eight-dimension Trellis-coded modulation (TCM), implemented through four Codex-proprietary VLSI chips and the powerful Motorola 68000 microprocessor. This combination furnishes the necessary power to achieve sustained error-free data throughput of 19.2 kb/s over most 3002 D1 lines, says the Mansfield, Massachusetts, firm.

TCM modems achieve their error-correcting ability by adding additional information to the transmitted sequence of signal points. In this way, error correction is achieved without reducing the data throughput. The Codex 2680 collects the data into 28 bits (four symbols) 2,743 times per second, and encodes three of the 28 bits through a 64-state convolutional encoder that adds an extra code bit. The resulting 29 bits are mapped into four signal points, each selected from a 160-point constellation, according to the Trellis coding scheme.

In going from the conventional two-dimension to an eight-dimension TCM, Codex reduced the size of the signal constellation from a possible 256 to 160 points. This enables the modem to perform error correction with the redundant signal points without introducing any additional susceptibility to line disturbances that would be created by a denser signal constellation.

Unit Comes with an Array of Diagnostics

To minimize downtime and optimize throughput, the 2680 comes with an extensive array of diagnostics. The Circuit Quality Measurement System displays major line parameters, including signal-to-noise ratio, receive level, and phase and gain hits on the control panel. In addition, an Error Probability Statistic that averages line-quality data gives the user a single measurement to determine the "health" of a line. A user can monitor, configure and test a remote modem from the control panel of a central-site modem.

The 2680 can also be operated under control of Codex's central-site network management systems, the DNCS and 4800 series. In the event of a line failure, the user can exercise the Dual Dial Restoral capability of the modem to establish a temporary dial-backup connection. This integral option includes auto-call/auto-answer capability that will ensure continual uptime.

The 2680 comes with a two-channel time-division multiplexer, with four and six-channel buffered multiplexers available as options. It's priced at $14,800. Other modems in the 2600 series transmit data at 4.8, 9.6, 14.4 and 16,8 kb/s.

In addition to the TCM coding technique used in the higher-speed models, the 2600 Series features a number of innovations, including automatic speed adjustment to changing line conditions for optimum throughput via the Codex-developed Adaptive Rate System, and downline program-loading of new options or customized features for improved product flexibility and reduced life-cycle costs.

For greater line optimization, the Train On Data capability enables the slave modems to synchronize to data on the line, rather than disrupting transmission to regain synchronization. To more accurately troubleshoot network problems, a Multipoint Signal Quality Binning feature identifies signal-quality data for up to 15 individual drops on a multipoint line.

Codex also has unveiled the first entries in a line of fully featured economy modems, the 2300 Series. Prices for the 4.5-kb/s Codex 2320 and 9.6-kb/s 2340 are $1,500 and $1,950, respectively. The modems employ quadrature amplitude modulation and an automatic adaptive equalizer to assure low error rates under the most-difficult transmission conditions. All controls required for routine operation of the stand-alone versions of the modems are located behind a fold-down front panel. An integral eye-pattern generator displays signal-point patterns on a user-provided oscilloscope. The modems also conduct self-tests automatically and allow the operator to isolate local, remote or line failures.

Recently the firm announced a new family of Bell-compatible modems, the Codex 2200 Series. These modems, which include the 2215, 2216 and 2217 models, operate up to 2.4 kb/s and offer Bell 202S, 202T and 201C compatibility, respectively. Furthermore, the overall size, complexity and power requirements for the microprocessor-based modems are significantly reduced. Prices are $495 and $425 for the 2215 and 2216, respectively, and $685 for the 2217.

Codex has also introduced a new family of high-end nodal processors that combine the advantages of multiplexing and packet switching in a single unit. Its first model, the Codex 6760, can support up to 256 concurrent calls and continuous throughput of 40,000 characters per second. Each 6760 node provides support for any combination of bisynchronous, asynchronous and HDLC/SDLC protocols. In addition, the processor supports the X.25 standards. Nontransparent protocol intervention is provided for IBM 2780/3780 RJE equipment. Ack/Nak acceptance commands are issued locally to prevent excessive round-trip delays, such as those encountered with satellite applications in the bisynchronous environment.

With the 6760, transmission efficiency is optimized by dynamically assigning bandwidth only to active channels. Asynchronous, bisynchronous and HDLC protocols are statistically multiplexed to gain the highest link-utilization efficiency. Using a distributed communications processor to perform traffic routing and switching functions in the network allows users to optimize the host and terminal resources. A minimum-delay-path algorithm assigns the most-efficient path available for optimum network operation, rerouting calls as needed to balance network load and compensate for line congestion on high-speed links to 64 kb/s. Also, the user-destination-routing feature of the 6760 allows async users to select and contend for compatible hosts in the network, increasing connectivity and utilization of host resources. A typical Codex 6760 system costs $45,000, including the software.

Datatel's latest synchronous time-division multiplexer combines up to six inputs for transmission over the Dataphone Digital Service network or conventional facilities at 9.6, 14.4, 19.2, 56 or 64 kb/s. Input channel speed is switch-selectable from 2.4 to 19.2 kb/s, and the DCP 9050 accepts any synchronous device. The units may also be used in a cascade arrangement to concentrate data from as many as 21 terminals over a single telephone line.

The bit-interleaving time-division multiplexer features individual-channel downline loading and extensive test and diagnostic capabilities. Input channels are individually programmable for operating parameters, including speed, code and timing options. Built-in diagnostics help pinpoint multiplexer, modem and line problmes. The DCP 9050 costs $2,150; the optional built-in customer service unit/data service unit adds $500 to the cost.

Last year, the Cherry Hill, New Jersey, firm also announced a T1 multiplexer for voice, data, facsimile and video applications. The DCP 9100 meets AT&T format requirements and may be used with its Accunet T1 service, as well as with microwave, fiber-optic, satellite, infrared and other private facilities. The DCP 9100 provides console control of the network from a central site. It accommodates up to 96 data channels, 46 voice channels or any intermix of the two. Data input may be synchronous or asynchronous, dial-up or dedicated, at speeds to 1,024 kb/s.

Switching Model Added to Line

Digital Communications Associates has upgraded its Netlink time-division multiplexer and added a switching model that allows individual channels or groups of channels to be assigned to various destinations throughout the network. Like its predecesors, Netlink II provides voice, data and compressed video transmission at speeds to 1.544 or 2.048 Mb/s and offers a number of new features: compatibility with any asynchronous ASCII terminal, as well as DCA's Network Management System, which allows a network manager to control the entire network from a central location using an IBM PC or PC XT; support of traditional drop-and-insert and bypass applications for multipoint networks; full redundancy of power, logic, T-carrier modems and facilities; support of independent trunk clocks for efficient satellite operations; support of D4 framing required for connection to AT&T's Accunet T1.5 service; and automatic time-of-day reconfiguration.

For voice transmission, Netlink II uses the companded continuously variable-slope delta-modulation technique that provides toll-quality voice reproduction at a 32-kb/s sampling rate. In a 44-channel version, Netlink II costs $5,795; a 20-channel unit sells for $4,195.

Switching Netlink performs all switching functions under the control of software commands that the network manager or operator enters from an operator's console. Network managers can store preprogrammed configurations for Switching Netlink to execute at the proper time or change channel destinations on line. The console also provides a central point for controlling all Netlinks in the network. Prices start at $6,295.

New Software Package Added

DCA has also enhanced its Series 300 network processors with a high-speed X.25 link and an Ethernet trunk, and added a bit-oriented protocol pass-through software package that allows the processors to transport SDLC traffic in an IBM SNA environment over a DCA trunk link. With this software, a DCA user can deliver SDLC transactions over either an X.25 link operating at 56 kb/s, or at lower speeds via DCA's own trunk link protocol.

In August, the Alpharetta, Georgia, firm added a 9.6-kb/s fast-pool model to its modem line. The DCA 932 employs light-emitting diodes and a liquid-crystal display to allow nontechnical operators to monitor operation, check signal quality and perform local and remote loopback tests. The operator can also observe and change both local and remote strap settings. All settings and speed changes can be downline loaded without a remote operator. An integral test-pattern generator and bit-error-rate detector add to the unit's diagnostic capabilities. The DCA 932 sells for $2,695.

DCA also offers a packetized modem that combines a multicarrier modulation scheme with digital signal processing and packet technologies to permit asynchronous operation at 10 kb/s over a dial-up link. Available as a stand-alone unit or as a printed circuit board for an IBM PC, Irmas' Fastlink can also operate as a 212A or 103-equivalent modem. It's based on a patented design of Telebit Corporation of Cupertino, California, that organizes information into packets to achieve the high-speed operation over ordinary telephone lines.

Gandalf Data has introduced five long-haul modems that broaden its Access series of dial modems and Fas Trak line of high-speed models. The microprocessor-based Access Series 212 is Bell 212A-compatible at 1.2 kb/s and Bell 103/113-compatible at up to 300 b/s. It offers auto-dial, auto long-on and auto-answer features and its nonvolatile memory can store up to 10 numbers with 126 digits/characters each. The Access Series 208 is compatible with Bell 208A or B modems and has auto-answer capability.

Joining the FasTrak line are the 96 and 96FP. Both operate in synchronous full-duplex mode at 9.6 kb/s with fallback speeds of 7.2 and 4.8 kb/s. The 96FP provides 8-ms fast polling and can also be used as a CCITT V.29 point-to-point modem.

Gandalf's fastest long-haul modem yet, the FasTrak 14.4, uses Trellis-coded modulation to operate at 14.4 kb/s over unconditioned 3002 lines. It's also compatible with CCITT V.29 modems at 9.6 kb/s. Prices range from $545 for the Access Series 212 to $3.950 for the FasTrak 14.4.

The Wheeling, Illinois, firm also has announced a second-generation local multiplexer, the Line Miser GLM 518, and unveiled the latest in its Line Miser data-over-voice multiplexer family, the DOV 640. Gandalf claims the DOV 640 is the first to operate synchronously at 64 kb/s, making it the fastest and the first to be offered in high-density rack-mount packaging with eight channels per card. Data is added to the telephone line above the voice band using time-compression multiplexing, which reportedly gives the DOV 640 features not available in frequency-shift-keyed models. It enables users to pass two control signals in each direction and provides remote digital loopback tests. Also, its digital technology allows for greater reliability. The DOV 640 supports synchronous data at speeds to 64 kb/s, or asynchronous data at up to 19.2 kb/s.

The Line Miser GLM 518 combines Gandalf's miniaturized short-haul modem technology with multiplexer techniques to support up to four or eight channels over privately owned four-wire circuits within a 2.3-km operating range. It operates asynchronously at rates to 19.2 kb/s and synchronously at 64 kb/s and can pass control signals per channel in each direction. The four-channel unit is priced at $525 and the eight-channel version at $800.

General DataComm's 14.4-kb/s modem also employs Trellis encoding for improved tolerance to line noise, backed up by fallback rates of 12 and 9.6 kb/s should line conditions deteriorate.

The DataComm 14400 is compatible with the firms's NetCon network-control system and also is compatible with its packaging concept, DataCommonality.

The Middlebury, Connecticut, firm also offers a full-duplex 2.4-kb/s synchronous/asynchronous modem, the DataComm 2412, and a "second-generation" Digital Service Unit, the 500 A/SR. Among the features of the 2412 is port security to protect confidential data bases, and a plug-in option that automatically retransmits data if a transmission error should occur. With the 500 A/SR, users can select one of three DDS speeds of 2.4, 4.8 or 9.6 kb/s from front-panel switches.

The company's newest modems include the 208B+/SD 4800-b/s switched-network modem and the GDC Multiport 14,400. The 208B+/SD offers a serial auto-dialing feature that allows terminals and host devices with SDLC and unextended HDLC protocols to make fully automatic calls. This capability reduces the costs and space problems associated with RS-366A ports and 801 automatic calling units. The modem can also accommodate a combination of both pushbutton and pulse-dialing systems on a single line connection, and provides 4800-b/s data transmission over two-wire, half-duplex switched networks. It's line-compatible with Bell 208B modems, supports point-to-point synchronous applications, and can accommodate either the ASCII or EBCDIC character codes on a switch-selectable basis. In addition, it's also compatible with the CCITT V.25bis standard.

The Multiport 14,400 is a 14,400-b/s modem that incorporates a six-channel, time-division multiplexer capable of supporting synchronous and asynchronous transmission over point-to-point private lines. The multiplexer is software-programmable by nontechnical personnel using English language commands displayed on a 32-character display. The TDM multiplexer channels can be configured to operate at speeds ranging from 2400 to 14,400 b/s. Options include aggregate-rate multiplexer configuration and individual channel settings. In addition, an alternative multiplexer configuration may be stored for donwline loading to remote modem locations. The unit offers a complete array of diagnostics that permit a quick analysis of the modem's operational status, immediate fault isolation and rapid system restoral.

IBM has expanded its product line with three high-speed modems that utilize large-scale integrated circuits to enhance reliability and reduce size. The 5811 limited-distance modem can transmit data over distances to 15 miles at synchronous rates of 2.4, 4.8, 9.6 and 19.2 kb/s. The 5865 operates at speeds to 9.6 kb/s with low error rates over unconditioned telephone lines, and the 5866 at 14.4 kb/s using the IBM-developed Trellis-coded modulation technique.

IBM Communications Network Management capability allows both modems to work in computer networks using IBM's Systems Network Architecture. However, the 5865 and 5866 can also determine problems with either incoming or outgoing lines without assistance from the host computer. A keypad and display are used to send and receive problem-determination and system-configuration information. In addition, all modems are available in stand-alone and rack-mounted versions. The 5811 sells for $595, the 5865 for $4,000 and the 5866 for $6,000.

IBM has also introduced two modems, the 3833 and 3834, that are 35-percent smaller, 40-percent lighter and cost less than comparable models of the predecessor 3863 and 3864 modems. At the same time, the company reduced the prices of the 3863 and 3864 by 13 to 29 percent, and the prices of the higher-function 3865 and 3868 modems by eight to 21 percent. The new shoebox-size modems are more reliable as well as more compact than the predecessor models, because of greater use of large-scale integrated circuits. Detachable cables and new troubleshooting aids make the modems reportedly easier to service.

The 3833 operates at 2.4 kb/s and the 3834 at 4.8 kb/s in synchronous networks. Both modems are fully compatible with IBM Communications Network Management and Problem Determination programs. The 3833 sells for $1,700 and the 3834 for $2,600.

IBM announced two modems for use with IBM PCs and other workstations at speeds to 1.2 kb/s. The stand-alone IBM 5841 modem is designed for use with IBM PCs and IBM 3161 and 3163 ASCII display stations. The circuit-card version is designed for installation in members of the IBM PC family. Both modems provide asynchronous data transmission in full-duplex mode at speeds to 1.2 kb/s. In addition, the 5841 allows synchronous transmission at speeds of 600 or 1200 b/s. The circuit-card modem costs $499 and the stand-alone unit $609.

Dial Backup Unit Introduced

Infinet has introduced the DBU 368 Dial Backup Unit to remotely restore communications in a data network by automatically bridging multipoint circuits and extending private lines beyond a failed hub site. The North Andover, Massachusetts-based firm describes the DBU 368 as a single card compatible with its DMX series of diagnostic modems.

The unit establishes dial connections using a speed-dialing feature and is activated by a command initiated through the EMS-II Network Control System console. The 368 permanently stores up to 10 sets of 22-digit numbers programmed by the network operator and may be located anywhere within the network, from central site to hub sites to several links embedded. It can test itself using the dial line to establish that the attachment to the dial line is viable before a critical situation occurs.

Other diagnostic features include soft straps for configuration that also verify detection of ringing signals, levels, and allow parameters like gain and transmit level to be remotely adjusted. Diagnostic information collectedd by the backup unit can be analyzed by the Infinet 90/60 Network Information System to determine trends and solve network problems. The unit's price is $995.

Infotron Systems has extended the network control features of its InfoStream T1 multiplexer with the introduction of its ANM 1500 advancedd network manager, reportedly the first system capable of managing and controlling multiple T1 networks from a single site. Consisting of proprietary software implemented in an IBM PC AT, the network management system uses advanced color graphics to report on as many as eight T1 networks with up to 16 nodes.

According to the Cherry Hill, New Jersey, firm, the 1500 is also the first T1 management system to provide dynamic monitoring of the networks, automatic alarm notification using real-time graphics, histograms showing events and utilization, and trouble tickets. It's a software-driven T1 multiplexer that can provide multiple-node networking at 1.544 Mb/s. It can also be used in single and dual-link point-to-point, drop-and-insert and ring configurations.

Remote Channel-Level Monitoring

The unit provides remote channel-level monitoring and other diagnostics, and can automatically reroute data or voice using a multilevel priority scheme. In addition, it can downline-load configuration changes without interrupting data on unaffected channels. The system also features dynamic circuit allocation that allows users to reallocate bandwidth based on several user-selectable priorities.

The ANM 1500 can manage from one to eight InfoStream networks, up to a total of 16 nodes, displaying a variety of network conditions in color. The system includes a variety of features to permit detection of a problem from a central location and immediate restoration of service through automatic alternate routing. Once service has been restored, users can review the systems' comprehensive event reports to isolate the problem, get a history of events leading up to the problem, and idenfity the restoration action that was taken.

The 1500 and its international counterpart, the InfoStream 2000, can be incorporated into extensive networks using other Infotron products, such as the IS 4000 intelligent switching system and the 990 NP network processor. The 990 NP is an intelligent nodal processor with tandem switching and alternate routing (TSAR) capability for automatically rerouting the data path in case of link failure or node congestion.

TSAR also increase network connectivity by allowing any terminal on any node to access any compatible resource on any other node. In addition, the firmwave-implemented TSAR greatly facilitates network setup and contributes to network security by enforcing privilege and access codes. The 990 NP can support virtually all protocols and multiple internodal high-speed links. It also supports host demultiplexing through its X.25 link.

International Data Sciences' Model 6400 data compressor permits a data throughout of 19.2 kb/s over two-wire, dial-up links. Termed the IDS Bullet, the data compressor incorporates a proprietary error-correction algorithm to provide error-;ree transmission. For the high throughput, the Bullet uses a sophisticated and proprietary artificial-intelligence data-compression technique. The system continually examines the data, gathers statistics and makes decisions for encoding the information. The encoded information continually changes as the data content changes, providing a highly secure and encrypted output data stream that the Lincoln, Rhode Island, firm claims is virtually impossible to decipher.

The unit has three modes of operation. In Mode 1, it may be used for data rate conversion; it's effectively transparent to the system with no data compression. Mode 2 adds error correction on the incoming data, while Mode 3 adds the adaptive data compression, yielding a fourfold increase in data throughput. All three modes are completely compatible with auto-dial, origination types and leased-line modems, according to the firm.

Micom Systems recently announced its fastest leased-line modem, the Micro-4000 Model 40168, that operates at speeds to 16,8 kb/s full-duplex. When used with the Simi Valley, California, firm's statistical multiplexers, such as the Micro800/- data concentrators, the modems allow the use of more terminals at faster speeds.

Trellis coding gives the Model 40168 the robustness to operate at the higher speed over lines that support only 9.6-kb/s operation using traditional modulation schemes. However, if line quality deteriorates below AT&T D1 conditioning standards, the modem can automatically fall back to 14.4, 12 or even 9.6-kb/s operation. When line quality improves, the modem automatically adjusts its operating speed upward. Model 40168 can also operate in CCITT V.29 mode at 9.6 or 4.8 kb/s to provide compatibility with older installed equipment. The 40168 is priced at $5,495.

Bit-Interleaving Multiplexer

NCR Comten has introduced a high-speed time-division multiplexer to support T1 carrier service with its 3690 communications processors. The bit-interleaving Comten T2033/2034 multiplexer lets network users link one or more Comten 3690 processors with circuits of 1.544 or 2.048 Mb/s to transmit data and digitize voice over the same T1 circuit. Available as a stand-alone unit or integrated in a 3690, the multiplexer can connect to multiple communications processors. It includes a hynamic-band-width-contention feature that allows specified ports to share a specific portion of the bandwidth on a contention basis.

When used with a console, the multiplexer provides users with communications line-management and diagnostic capabilities, including the ability to configure or reconfigure the multiplexer from a local or remote console; to display multiplexer, channel trunk and remote-site statistics; and to perform diagnostic tests on the multiplexer. An additional line-management feature lets users reconfigure inactive ports while the multiplexer is in operation, without affecting active ports.

The St. Paul, Minnesota, firm has added a small-scale communications processor to its product family and unveiled new models of the Comten 7160 series of diagnostic modems. The Comten 5620 extends full-scale communications-processor capabilities, such as application switching, routing, polling, automatic dialing, error recovery and data concentration, to users' small or remote network sites.

According to the firm, the 5620 is the first of a new generation of communications processors. They consist of a set of modular components that, when fully configured, can support up to 32 full or half-duplex communications lines and one or two host computers. The unit features VLSI technology for high network reliability, low power consumption and a small footprint. The processor can operate in a standard office environment and features comprehensive built-in, self-test programs that isolate faults to a specific board so that repairs usually involve replacing only one board.

On-Line Diagnostic Information

The Comten 7160 Commander series of modems features a 32-character LCD front-panel display that provides SNA and non-SNA network users with on-line diagnostic information. To help operators isolate line and systems failures at the local and remote modems, the display presents 11 message types indicating modem and line characteristics, status, signal quality and configuration details. Three models are available: the 7164-0100 is a 4.8-kb/s dedicated-line modem for point-to-point or multipoint configurations; the 7164-0200 is a 4.8-kb/s switched-line modem; and the 7165 9.6-kb/s modem can alternate between point-to-point and multipoint networks with one switch setting. Prices for the 4.8-kb/s models start at $3,700 and for the 9.6-kb/s unit at $5,800.

Paradyne has added both high and low-speed modems for dial-up applications to its product mix. Its fastest switched-network modem, the HDX 12000, operates at 12.2 kb/s in half-duplex, point-to-point applications. It features a data-transparent error-detection algorithm that derives an additional 3 dB of operating margin under impaired circuit conditions and provides automatic fallback operations at 9.6 kb/s. The modem's microprocessor-based design controls all signal processing functions, including automatic adaptive equalization, filtering and demodulation. Built-in monitors, including an eye-pattern generator, provide rapid isolation of hardware and circuit impairments.

The 9.6-kb/s HDX 9600 provides automatic fallback operation with on-line compatibility with 208B-type modems at 4.8 kb/s. When communicating with a 208B-type modem, the HDX 9600 automatically adjusts its signaling format to 208B. This allows existing 208B networks at 4.8 kb/s to be upgraded to 9.6 kb/s without affecting current services. The HDX 12000 costs $3,600, the 9600 costs $1,995.

Auto-Dial Modems for Full Duplex

At lower speeds, the Largo, Florida, firm now offers auto-dial modems for full-duplex operation at 1.2 and 2.4 kb/s. The 2.4-kb/s FDX 2400 sells for $805, the 1.2-kb/s FDX 1200 for $365. Both modems automate call connection, information transfer and disconnection for synchronous or asynchronous host-to-terminal or terminal-to-terminal applications. In the command mode, the user can enter, change and verify configuration parameters at any time. Both default and user-defined parameters and telephone directory information are stored in memory and are not affected by random or sustained loss of power.

Paradyne has also extended network management to its multiplexer networks with a multiplexer control option for its Analysis network management system. The option gives network managers simplified and full-functional control of the network from a single menu-driven display. It operates in a network of Paradyne DCX 850 or 840 multiplexers and combines in one unit a network supervisor, event-log mapping and test-panel functions.

The option also provides central-site configuration backup. It works with the firm's Analysis 550, which monitors small networks with up to 512 devices, or the Analysis 5500, which supports configurations of up to 2,000 devices. The option is priced at $2,500.

Racal-Milgo offers the first in a series of fiber-optic data communications products, the Omnimux 3200 fiber-optic time-division multiplexer. Designed for both asynchronous and synchronous data as well as digitized voice traffic, the multiplexer can accommodate up to 32 ports at channel rates to 64 kb/s.

By multiplexing over fiber-optic lines, the Omnimux 3200 provides the high data throughput at much-lower error rates than coaxial or twisted-pair lines in standard, electrically noisy or chemically hostile environments. Its fiber design, virtually impossible to tap, also provides secure data transmission.

Ideal for campus-like or single-building environments where fiber is already in use, the protocol-transparent multiplexer provides efficient and economical local-area communications at distances to six miles without repeaters. System management and diagnostic control are provided through an operator-friendly supervisory terminal that allows access to front-panel functions for up to 99 multiplexers. The basic eight-channel unit costs $5,390.

The Sunrise, Florida, firm has added to its multiplexer line the Omnimux 82 series of low-cost statistical multiplexers with diagnostic and control capabilities. Available in capacities of 8, 16 or 32 channels, the multiplexer handles asynchronous and synchronous data at aggregate link speeds from 1.2 to 72 kb/s. Prices range from $2,026 for the eight-channel unit to $5,957 for the 32-channel model.

Racal-Milog also announced an interface for the Omnimux 82 series that allows the units to be monitored and controlled through the firm's CMS network diagnostic and control systems. In addition, it introduced a series of diagnostic Data Service Units. Operating from 2.4 to 56 kb/s in point-to-point or polled multidrop DDS links, the DSU RD 500 and 556 can be controlled from any ASCII terminal, or from Racal-Milgo control terminals and multiplexer controllers.

Among the latest additions to the firm's Omnimode series of intelligent microprocessor-based modems are the Omnimode 1614, which operates at 16.8 kb/s, and the Omnimode 14.4, which now incorporates CCITT V.33-compatible modulation and training sequences for operation at 14.4 kb/s. The 1614 automatically selects the highest operating speed that telephone-line quality allows. As conditions change, the modem will down-speed from 16.8 to 14.4 or 12 kb/s, as required to provide the best-possible performance on that line.

The modem also features a front-panel information and control center with touch-sensitive switches for changing the modem speed, configuration, transmit level and strapping. A remote modem-control option is also available to extend the same capability to remote sites. The Omnimode 1614 is priced at $10,000.

Racal-Vadic continues to pioneer with 212A-compatible modems. Its 1200 PA model reportedly solves virtually every application problem encountered with today's dial-up modems. Starting with basic features such as 212 and 103 compatibility, AT2 (Hayes) dialing, automatic answer and originate, and complete diagnostics, the modem adds error control, network control and security within a compact package. It incorporates Modem Manager, a Racal-Vadic facility for network control that enables a network manager to read and change options, phone numbers, log-on messages and security orders over telephone lines. The modem also has built-in MNP error control.

"We have identified all the capabilities useful at 1200 b/s and put them into one modem," claims Keith Peters, product manager. "At the same time, we've developed the most-compact package in thed industry." The modem sells for $495.

Racal-Vadic also added MNP error-control and speed-conversion to the 2400 PA modem, allowing it to operate at 300 and 1200 b/s as well as 2400 b/s. In addition, the Milpitas, California, firm has introduced what it claims is the only auto-dial 2400-b/s modem compatible with the IBM Bisync communications protocol. The 2400-S is a full-duplex synchronous modem that provides dial-up, unattended communications for IBM 2780/3780 remote job-entry systems.

The firm recently introduced a dial-up modem, the 9600 VP that operates at 9.6 kb/s with error control and data compression. It offers automatic originate and answer, front-panel dialing and diagnostics, software-configurable options, and support for Racal-Vadic and extended AT dialing-protocol command sets. While compatible with Bell 103 and 212A standards, the 9600 uses a CCITT modulation technique and Racal-Vadic's Data Link Protocol at higher speeds.

Racal-Vadic's 7400 Series statistical multiplexer is a four or eight-channel, menu-driven multiplexer with several innovative features: a 2.4-kb/s switched-network internal-modem option; a leased-line internal modem with automatic dial backup and restoral; and an extended system-control function accessed through a 300-b/s "help" diagnostic modem. The integral 2.4-kb/s modem allows full-duplex operation over the switched telephone network, eliminating the need for leased lines.

If a problem develops, the "help" modem calls a pre-set telephone number to inform the system manager what the problem is. Conversely, the system manager, a field engineer or other appropriate party can call the modem from anywhere in the world and gain access to the supervisory mode. The four-channel model sells for $1,295, the eight-channel with both 9.6 kb/s and "help" for $3,410.

Voice/Data Mux Introduced

Timeplex recently introduced a voice/data multiplexer that combines information from up to seven synchronous data ports and a PBX voice port over a single link at speeds of 56 or 64 kb/s. The Voplexer incorporates a sophisticated, yet user-friendly supervisory port that permits complete programming of port and data-link parameters. A series of menus, several requiring operating passwords for access, lead the unfamiliar user through programming, diagnostics and unit configuration. The familiar user can change parameters via direct commands. The Voplexer supports data-port speeds of 1.2 to 19.2 kb/s.

The Woodcliff Lake, New Jersey, firm has also upgraded its statistical multiplexer line with the Series III Microplexer family that includes a variety of compatible switching and non-switching models available with up to 8, 24 or 48 asynchronous or synchronous data ports. These models can be supplied with one to four composite data links that will run at up to 19.2 kb/s each.

Series III multiplexers can also be used with the firm's Prophet network manager for single-site network control and management. For higher-speed operations, the firm's Link/1 facilities management systems support multiple T1 links with single-point network control over port-to-port switching capabilities.
COPYRIGHT 1986 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1986 Gale, Cengage Learning. All rights reserved.

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Author:Edwards, Morris
Publication:Communications News
Date:Jan 1, 1986
Words:7174
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