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Testers Rise to the Challenge of Complex Communications World.

Responding to the challenge of divestiture and deregulation, and the growth of multi-vendor networks, suppliers of data test equipment are making their devices smaller, lighter, more capable, easier to use and less expensive. Today's models stress portability and the flexibility to accommodate a wide variety of network environments. There's also a move to higher-speed operation and the ability to function with bit-oriented protocols, such as High-level Data Link Control (HDLC), specified in the X.25 standard, or IBM's Synchronous Data Link Control (SDLC).

Reflecting the scarcity of technical personnel and the complexity of modern communications equipment, most analyzers feature menus with "help" functions to prompt the user through the testing or diagnostic routines. They can also be programmed to trigger on certain occurrences so that only critical data is trapped for analysis, in contrast to passive monitors, which strap data indiscriminately. As simulators, intelligent devices allow users to perform interactive tests in a variety of simulated network operating environments. Also, the units can provide a more-thorough testing of hardware and software by simulating error conditions not possible with standard network components and systems.

many units also gather network statistics, or perform simpler tasks of bit- and block-error-rate testing. However, there are a number of less-expensive units that are specifically designed for such tests. In addition, there are several systems for measuring the quality of the telephone line for data transmission.

Developments in Test Equipment

What follows is a rundown on recent developments with protocol analyzers and simulators, and various other types of data test equipemtn:

atlantic Research has added an advanced SNA protocol trace capability to its Comstate II protocol analyzer, giving the operator a clear, detailed picture of the SNA protocol. Translation charts or manuals are no longer needed because the code translations are built into the Comstate II; the operator simply makes a couple of menu selections and the analyzer does the rest. Also, the user can flip back and forth between the raw data display and decoded SNA screen with the press of a key.

All frame-identifier types are decoded, and frame, transmission and request/response headers displayed. More than 130 different request/response units are identified and displayed, and bind commands are fully expanded. Also, sense information is displayed when the Sense Data Indicator bit is set. To pinpoint specific problems quickly, the analyzer allows the operator to choose the type of information he wants to see. Comstate II also analyzes and emulates SDLC, HDLC, X.25, Bisync, isoc and async. In addition, the Comstate II has been certified--along with its companion unit, the Comstate I--for X.2 applications.

In April, the Alexandria, Virginia firm added seven features to the Comstate I, including unattended remote control and Automonitor setup. In addition, the analyzer is reportedly the first that will automatically call the user back when the problem is found. Explaining the reason for the feature, Lightsey Wallce, vice president and director, product planning, notes that random transient problems are seldom found on the first visit. They also represent significant on-site personnel costs, as well as delaying the repair.

"The Comstate I offers substantial cost savings because it may be left unattended on site and will automatically call a central-site support specialist," according to Wallace. "one specialist can not effectively troubleshoot many sites, because analyzers in the field only call in when the condition being looked for occurs. A history of line data is also available indepth analysis."

Atlantic Research has also added the automatic callback feature to its Intervew 40B data analyzer, along with Automonitor, unattended remote operation and other new features. The Automonitor feature provide fast automatic configuration of the tester and automatic display of data at the pressing of the RUN key. The 40B examines data on the circuit and determines the protocol parameters for the most-accurate automatic configuration available. The unit will automatically monitor and configure itself for speed, format, code, parity and block check type. With external clock, the unit handles data rates to 72 kb/s, or 19.2 kb/s with internal clock.

Last fall, the firm also upgraded the Interview 4600 data analyzer with new software for in-depth analysis and testing of networks using high-level DDCMP and X.25 protocols. The 4600 allows the user to display frame and packet-level control information in an easy-to-read format. There is no need to enter complex trigger strings byte-by-byte, bit-by-bit to detect specific events at the frame or packet level. For emulation, easy-to-use menus allow the user to transmit any type of frame or packet-level message by simply making a few selections.

In May, Atlantic Research announced inter-family communications for data and programs between its Interview and Comstate models. All units can receive and display CRT buffer data from any other unit, and programs can be remotely transferred between all units. In addition, each analyzer now offers ASCII terminal mode, permitting remote control of the Interview 30B and 40B and the Comstate I. Each programmable menu in these remotely controllable units can be accessed, changed or executed by any new Interview or Comstate test equipment or ASCII terminal.

Avant-Garde Computing has broadened the use of its Net/Alert software-based performance monitoring system to encompass small as well as large networks. The system monitors the status, performance, availability and utilization of dedicated leased-line networks, using color graphics to alert operators to the location and nature of problems. Net/Alert Level 3 provides comprehensive network monitoring, analysis and management for up to 4,096 lines, with real-time graphics, printed reports and a historical data base. Level 2 offers all the dynamic capabilities of Level 3, but without the historical data base, while Level 1 provides basic inquiry monitoring for networks up to 32 lines. Net/Alert Level 1 is modular and fully expandable to both Levels 2 and 3.

Historical Perspective Provided

By gathering and storing traffic measurements, Net/Alert provides an historical perspective for isolating, investigating and resolving recurring problems. On the one hand, network managers can identify and resolve traffic bottlenecks that slow down the productivity of the network's end users; on the other, they can save money by locating and eliminating under-used terminals and communications lines. Net/Alert permits monitoring by application and transaction type, according to David Hunter, manager of marketing and communications for the Mt. Laurel, New Jersey firm. "Thus, planners, operators and managers can monitor the kind of work done on each terminal or transmitted through the network, and compare the performance of the physical network with the performance of specific applications," he says. Such application monitoring highlights software performance and host load problems, Hunter notes, making it easier to balance and fine-tune the network.

Avant-Garde also offers a response-time monitor for individual terminals, called Tempo. The unit plugs into the terminal and forwards the performance statistics to the host for processing and report generation. Another product, Net/Guard, controls network access by personal computers and other dial-up devices, while at the same time monitoring the network utilization and performance so that managers know who's doing what, when, why and for how long.

Digilog's X.25 protocol analysis system recently became one of only two such systems to receive GTE Telenet certification, and reportedly the only one that provides complete DTE and DCE analysis. Designed to allow users to perform accurate fault analysis and testing of X.25 software and devices, the X.25 analysis and emulation software is contained on a micro diskette that runs on either a Digilog Model 600 or 800 automatic protocol/performance analyzer. The programs convey operation status, test results and performance statistics via the data analyzer's CRT screen.

Protocol testing is an important trend, says John Bennett, director of product marketing for diagnostic products with the Montgomeryville, pennsylvania firm. Bennett points out that the International Organization for Standards recently recognized that incompatible implementations of the X.25 protocol could result in an unacceptable expense to the X.25 network users and equipment suppliers. "We have had our eye towards the certification since our model 600 and 800 protocol analyzes were in the development state," he says.

Introduced last year, the model 600 and 800 are the top-of-the-line members of a four-model family of automated protocol analyzers. All four analyzers feature automatic protocol analysis and interpretation capabilities that isolate the fault and describe the nature of the malfunction in plain English on the CRT screen. Roy Gemberling, vice president and general manager of the Digilog Network Control Division, claims the analyzer family was designed to accommodate today's bit-oriented multilevel protocols and faster transmission speeds. "Sophisticated hardware and software automates many of the monitor and test functions," he says, "so that first-time users can perform like experts and seasoned professionals can do a lot more, faster."

The analyzer family ranges from the small, lightweight model 200 with its removable EEPROM (electrically erasable programmable read-only memory) packs, automatic setup and full protocol decodes, up to the powerful 800 with its 10-megabyte Winchester disk, color CRT, Sony micro floppy and multilevel program operation. The 200 is targeted for the entry-level user, with such features as menu-guided operation, fill-in-the-blanks programming and English-language prompts and help screens. These features and such capabilities as automatic setup and interchangeable EEPROM packs help make monitoring analysis and the testing of lines, modems, terminals and software a pushbutton task. The model 400 offers 56-kb/s operation and an optional built-in micro diskette, along with more programming flexibility, to expand its automation capabilities. With the model 600, the product emphasis shifts distinctly to power, versatility and speed. All capabilities are fully functional under program control at line speeds of 72 kb/s. The unit is equipped with a built-in micro diskette, and has six soft-function keys and a seven-inch CRT. The model 800 operates at 256 kb/s, is equipped with a 10-Mb Winchester disk and has nine soft-function keys and a 10.5-inch color CRT.

Analyzer Decodes Many Protocols

Besides the X.25 protocol analysis software, the 800 runs software for line-utilization studies and network performance analysis, using color graphics to display the statistics on the screen. According to Bennett, the model 800 decodes more protocols than any other unit, including HDLC, X.25, SDLC, ADCCP, Bisync and DDCMP. In addition, the 800 can completely simulate either end of the circuit, DCE or DTE. It is also equipped with six comprehensive bit-error-rate tests to provide pushbutton checking of telco facilities and modems. Because the model 800 and other members of the analyzer family can be remotely controlled from any other Digilog protocol analyzer, users can view data, run programs, print reports and perform all other functions from one site.

Digitech Industries or Ridgefield, Connecticut, also introduced a protocol analyzer family early this year in three configurations for different levels of users. With the Series 500 analyzer, users can upgrade the software and hardware of each model should their requirements become more rigorous. Each model can monitor, emulate and analyze network performance at speeds to 72 kb/s, full duplex. They can also record data at speeds to 256 kb/s, full duplex. The use of a soft-key-based trigger programming language with the portable units lets users build a virtually unlimited number of trigger statements, using simple-English sentences. All statements can be run simultaneously. These "when-then" statements can be used to send special messages, higlight data and lead conditions, selectively store data for cutomized tests and detect error conditions. For simplicity, the analyzers combine dedicated function keys and eight soft keys with a menu-driven system. All models can be operated remotely to permit central-site control of diagnostics. They may control or be controlled by another Series 500 unit, an ASCIi terminal or a personal computer with communications capabilities.

Model 500 operates with all popular bit- and byte-oriented protocols and comes equipped for intelligent network monitoring, emulation and diagnosis. The model 520 provides a 10-Mb Winchester hard disk and a C compiler for advanced programming. Prices start at $12,900 for the model 500, $15,500 for the 510, and $18,500 for the 520.

dynatech Data Systems of Springfield, Pennsylvania, offers a number of portable testers with menus that give users quick access to basic tests, a large buffer to store data and an external video output and hard-copy port. Its Dyna-Test 2000C protocol monitor and simulator includes a CRT, tape cartridge and full keyboard in a compact, 31-pound unit. It features a real-time, split-screen display that shows frame and packet data in clear text. A tape cartridge can record 200,000 characters of data, as well as progrms. In menu mode, users employ a multiple-choice question-and-answer format to select the appropriate test. A 1K-nonvolatile memory holds user programs when the power is off.

The companion Dyna-Test 1600 features one-button setup and 56-kb/s real-time recording. Up to seven test parameters can be recalled at the touch of the button. Also, you can establish and revise these parameters on line without stopping the unit. The protocol analyzer monitors synchronous and asynchronous data supporting SDLC, X.25, Bisync and DDCMP protocols. It handles all common interfaces, including RS-232/V.24, V.35 and RS-449, at speeds to 100 kb/s. Its transmit capability permits emulation of both DTE and DCE.

Dynatech's Simon 5 protocol simulator/monitor also uses a menu approach with powerful soft keys, a HELP key and a disk-based training system. simon's diagnostic capabilities are divided into four operating modes accessed through a single key. Menu mode lets users select parameters to emulate different protocols. Trapping, event couting, transmission tests and bit-error-rate tests are standard menu selections. Protocol mode previous single-key access to eight sets of tests and the I/O parameters needed to operate them. Program mode allows users to edit and execute programs for such specific needs as developing communications software, troubleshooting problems and evaluating network hardware. Scroll mode lets the user view data captured from line or disk. simon 5 operates at data rates to 64 kb/s and sells for $17,950. The Dyna-Test 1600 with tape drive sells for $8,750, and the Dyna-Test 1600 with tape drive for $13,800.

Halcyon's latest data link analyzer, the model 880, offers menu-driven operation with full prompting and 240K of data capture in a compact unit weighing less than 20 pounds. For ease of use, the 880 employs the firm's Automonitor, which simplifies setup, and it presents X.25 and SNA protocols in easty-to-start/stop triggering on strings, bits, EIA line status, errors or time out. A convenient counter page keeps track of useful network statistics. The 880's capture buffer stores link data at rates to 110 kb/s, and one can write up to 1.3 Mb of program code or data to the 880's built-in quad-density micro floppies. The 880 connects to any auxiliary equipment that uses an RS-232-C port, and master/slave communications software is standard. Complete with built-in printer driver, the 880 data link analyzer sells for $13,995.

Ease of use is also characteristic of the 801B data monitor and emulator that the San Jose, California firm introduced last November. Using Automonitor, the 801B identifies the speed, protocol, bits-per-character and line parity automatically. The units monitor full-duplex data at rates to 56 kb/s. Powerful start/stop trapping capability and 33 function-design counters can be used to record the occurrence of specific events and to gather data link statistics. The 801B analysis capability provides detailed breakout of X.25, SNA and DDCMP protocols into English mnemonics. In August, Halcyon also unveiled a new signaling package compatible with its 701A, 704A and 704A2 transmission test sets, which allows E&M I, II and III signaling or loop dial-and-talk capability. The unit costs $795 if purchased with a 701A or 704 test set, and $1,495 if retrofitted.

Hekimian Laboratories recently introduced a family of digital communications test equipment that provides remote performance monitoring and testing for DS1, DS0 and subrates carried on T1 facilities. The Digital Test Access System comprises two groups of equipment, each designed to perform all test and monitoring functions of the T1 or lower data-rate lines, either on location or from a remote test center. the DS1 Test Access Unit (DTAU), which is designed for use on T1 facilities carrying High-Capacity Digital Services at the DS1 rate, provides for non-intrusive monitor access with continuous scanning of all assigned T1 lines. The unit monitors bit-error rate, and checks for loss of signal and "all ones" condition. When it detects abnormal performance, a message is automatically sent to a local or remote testing location.

In combination with the DS1 Performance Unit (DPU), the DTAU can be used for continuous monitoring as as intrusive testing of the DS1. Service tests that can be performed include bit-error rate, frame slips, error-free seconds, frame sync lost seconds, severely errored seconds, framing bit errors and CRC-6 or block errors. The DPU operates in no framing, superframing and extended superframing modes and can generate CSU loop up and down codes in either or both directions.

Similar tests of channelized DTAU+, which access T1 lines without errors, and inserts test signals into selected channels without disrupting the other channels or causing reframes. Full channelized testing can then be accomplished using Hekimian 3700 or 3900 communication test systems. Any configurations of the test equipment can be controlled either from a local terminal or remote controller. Standard RS-232-C interfaces can also be used to integrate the control into Hekimian React remote access and test systems.

In July, the Gaithesburg, Maryland firm unveiled a T1 carrier test module as an option to its model 3900 communications test set. The model 3962 can be used in line for testing a defective T1 carrier channel, while allowing the remaining 23 time slots to pass through undisturbed in both directions, so that a single channel can be tested without disrupting the entire T1 link.

Hewlett-Packard recently added software and hardware features to its HP 4951 protocol analyzer to accommodate popular protocols. among the new offerings are an SNA analysis package, an asynchronous terminal emulator program, an X.25 package, an X.21 interface kti and a DDCMP decode and simulation package. Also, a new video-output port enables users to hook up the analyzer to a video monitor for a larger picture of what appears on the analyzer screen. In addition, a separate RS-232-C/V.24 printer or remote port enhances the remote-testing capability of the HP 4951 while letting users transfer data, programs and applications to any member of the protocol analyzer family. The asynchronous terminal emulator equips the HP 4951 for communications with any asynchronous device. The HP 4951B protocol analyzer sells for $3,995, with an additional $850 for the optional integral mass-storage tape cartride.

Bit-Error-Rate Test Set Is Newly Enhanced

Hewlett-Packard has also enhanced the HP 4925A bit-error-rate test set to handle Dataphone Digital Service circuits that employ V.35 interfaces. Among the measurements the HP 4925B can perform are evaluation of bit-error rates, errored seconds and percent error-free seconds on synchronous and asynchronous networks, parity-error counting and RTS-CTS delay time. The unit also handles startup tests and Fox message transmission in Baudot, EBCD, ASCII and EBCDIC codes with simultaneous parity-error analysis on received data. The HP 4925B sells for $1,195.

International Data Sciences' 5000 Series of test equipment uses plug-in software and interface modules so network managers can customize the units to their testing requirements. Each member of the test equipment family can function independently and also can communicate with all of the other members. For example, the model 5300 network and protocol analyzer at a central office can transmit test software over any asynchronous data link to either a model 5100 hand-held test set, a model 5200 multi-speed test set, or another 5300, and run unattended tests by remote control. All test results and data can then be transmitted back to the 5300 at the central office, where data and test results can be analyzed and reviewed.

The model 5100 is a microprocessor-based, hand-held test set that supports speeds to 64 kb/s. the portable unit can perform bit- and block-error-rate tests, error-free seconds test, DTE emulation, point-to-point or multidrop polling, and trap and monitor tests. Function module capability can be down-line loaded to it by a model 5300, and it can up-line load setup information, data and test results. Test software is packaged in convenient function modules, which come with a color-coded label that corresponds to the 5100's front panel. This label defines the function/setup keys, indicator LEDs and all of the available modes for that particular module. Test results, setup information and data are displayed on a high-resolution, 48-character LCD display with contrast control. Interface modules include RS-232-C, RS-449, V.35 and DS1.

The model 5200 supports data rates to 10 Mb/s and comes with two high-resolution LDC displays; a 48-character LCD display presents setup parameters, test results and data, while an additional four-digit LCD display allows the user to show the date, time, frequency of the transmit or receive clock source, or either of two event counters. The model 5300 comprises a PC adapter board, an external interface adapter and the IDS application software to convert an IBM PC, PC-XT or PC Portable into a programmable network and protocol analyzer. User-menu selections and corresponding "help" screens guide the operator through teh testing procedures. With the IDS Datasolve programming language, tests can be programmed for a variety of applications. The 5300 has an automatic setup feature and it can down-line load function module capability, up-line load test results and data, and remotely ontrol any member of the 5000 Series.

IDS has also added to its line of hand-held testers a unit that the Lincoln, Rhode Island firm claims breaks the size barrier for high-speed test sets and the speed barrier for hand-held test sets. Model 66 measures 6.8 by 8.1 by 2.3 inches and weighs less than three pounds. It can operate from one of four internally provided data rates, or from an external clock at rates of 10 Mb/s. Four plug-in interface modules support RS-232-C, RS-449, V.35 and DS1 applications. Model 66 performs bit- and block-error rate, errored seconds and sync-loss tests, and can generate, transmit, receive and analyze either of two pseudo-random test patterns. It sells for $1,295.

Navtel of Boca Raton, Florida, has added a communications analyzer for protocol, data and network link testing at rates of 72 kb/s. The DataTest 5 performs frame-level decoding for HDLC and SDLC and handles ASCII, EBCDIC, EBCD, Baudot, Ipars and Hex codes. It permits simultaneous bit- and block-error-rate testing with 17 other tests, including distortion testing and a polling test for up to 32 stations. The unit can be programmed via state programming in four ways: through menu-guided steps, via a BASIC program, via state programming or through a program of key codes that the instrument interprets as keyboard entries. In the "state" method, sets of events and actions are grouped as states. A state is similar to the "trigger" concept, but evaluates up to 256 events simultaneously, and each event within a state can consist of multiple conditions. Mark Johnson, marketing manager, notes that this allows multiple tests to be run simultaneously and most-closely models the ISO protocol definitions.

The DataTest 5 comes with a 640-character back-lit LCD display, and 64K of capture memory and 10K of nonvolatile storage for user-definable messages. Interchangeable interface pods handle RS-232-C, RS-449 and V.35 applications, among others. The basic unit sells for $4,995. Standard options include three-level X.25 or SNa capability, integral mass storage modules, an integral printer and a video output crd.

northern Telecom recently added a performance monitor and an integrated data monitor feature to increase the data-handling and control capabilities of its Network Management System (NMS). Developed by the firm's Spectron Division, the NMS is a module-processing system that provides centralized control of switching, test and performance subsystems that handle network test and control functions.

Monitor Checks Network-Wide Communication Lines

The performance monitor checks and analyzes network-wide communications lines controlled by the matrix switch. The NMS loads and controls the performance monitor, which automatically adapts to various protocols, including Univac and IBM 3270 Bisync and SDLC. Support for X.25 will be available in the near future. In scan mode, the monitor can check a single line or a series of lines. Its auto-baud features operates at transmission rates up to 19.2 kb/s.

The integrated data monitor feature allows operators to view data moving across the split screen of the NMS console monitor. Information showing real-time network status is displayed on the upper portion of the screen, and control information on the lower portion. The new feature allows the operator to monitor the real-time display of data transmission on any line that runs through the matrix switch, eliminating the need for a dedicated screen. All NMS systems can be upgraded to include the new feature, according to the Marlton, New Jersey firm.

Tekelec has enhanced its Chameleon protocol simulator/analyzer with a real-time clock board, three new protocol-support software packages and 12 upgraded ones. Operation of the Chameleon II tester has also been made easier by including real-time analysis, automatic program loading, automatic remote functions and simplified menu presentations. The real-time clock board provides time-stamping with millisecond accuracy in analysis, trace and simulation. The new software programs designed to function with the board are SDLC Statistics, X.25 Statistics and Direct-to-Disk Analysis.

The X.25 Statistics program supports Modulo 128 and extended addressing, as does the firm's X.25trace and SNAtrace and SNAtrace analysis packages--important for networks using satellite links. Like X.25 Statistics, the SDLC Statistics program monitors the line and counts all frames by their mnemonic names, individual valid and invalid frames, and CRC errors. Statistics logs may be printed out unattended at set time intervals. Direct-to-Disk Analysis software allows X.25 and SNA/SDLC data to be streamed directly to the tester's two Sony 3.5-inch micro-floppy disks. The software enables nonstop data acquisition at up to 64 kb/s with all triggers active. enhanced simulation trace capabilities permit data to be played back through the X.25 or SNatrace for complete interpretation of all frames and packets in X.25 and all levels of SNA/SDLC.

As an analyzer, the Chameleon's key features are its vertically split screen display, which allows engineers to view the data communications from both sides of the link simultaneously, and high-speed triggering, which enhances the user's ability to check a device's operation without shifting through overwhelming amounts of data. A library of over 250 tests has reportedly been created for the Chameleon II to test a device's adherence to X.25, IBM SNA and Bisync protocols. The basic unit is priced at $19,500.

The Calabasas, California firm also combines a DS1/T1 frame simulator and analyzer into a portable package, the TE-820A. The unit thoroughly exercises switch hardware and software at 1.544 Mb/s, providing complete channel access to data, framing and signaling bits. Designed to test new-generation digital switches such as the 5ESS, it can also put a wide range of other equipment through its paces, including channel banks, T1 multiplexers, large PBX installations and digital speech interpolators associated with earthstation equipment. Prices start at $9,500.

Tektronix, of Redmond, Oregon, has added two models to it's 830 Series communications analyzers to provide greater speed, expandability and versatility. Both units cover the entire spectrum of the line monitoring, data link testing and interactive exercising and simulation in a wide range of network environments, from Bisync to custom programs. the 836 operates at speeds at 72 kb/s, and the 835 at rates to 19.2 kb/s full duplex.

Increased capabilities include upload/download, nonvolatile memory and multiple triggers. Users can scroll through captured DTE data or DCE data only, in non-real time, and transfer the current frame of the capture buffer to a message buffer under program control. The 836 costs $4,650, and the 835, which is fully upgradeable to the 836, costs $3,350.

Telecommunications Technology recently unveiled a portable, battery-operated test set that provides all transmission quality testing, signaling simulation and return-loss testing capabilities required for network demarcation testing, effectively replacing three instruments with one. Since the 1180 can simulate PBX or station and network signaling, it is also useful for both PBX and circuit installation testing to verify that transmission and signaling parameters are correct.

Microprocessor-controlled, the 1180 uses an 8 by 30-character liquid crystal display and soft control keys, and includes menu-driven tests. As a result, operation of the 1180 is easy to learn, and tests can be set up quickly. Front-panel jacks provide connection to the circuit under test, including transmit, receive and signaling pairs, and allow connection of a portable test set. The unit is priced at $4,795.

In addition, the Sunnyvale, California firm has added trunk-testing capabilities to its Switched Access System that are compatible with those used by AT&T and the Bell operating companies. The SAS 105 trunk-testing system automatically conducts two-way measurements of loss, noise, return loss and gain slope. it also compares measurement results against two sets of limits--"maintenance" and "immediate action"--and generates appropriate acception reports. The trunk-testing system comprises three parts: a computerized management and control subsystem, a trunc-access/measurement controller, and a far-end responder.

Because the system can interact with AT&T/Bell responders, users can also test foreign exchange, wide-area telephone service, and central-office trunk lines. the SAS 105 also measures the transmission quality of each link, giving companies greater control of their circuits and possibly eliminating the need for engineers at remote sites.

Universal Data Systems' Comtest 200 data line monitor and emulator supports synchronous and asynchronous data in a variety of code sets, protocols and bit rates to 19.2 kb/s. with a few key-switch depressions, users can determine the bit rate, bit/character, parity, jitter and bias distortion for an asynchronous network. Synchronous network parameters can also be determined with limited operator involvement.

For network emulation, operators can use a programming language developed by the Huntsville, Alabama firm to provide capabilities ranging from interactive terminal simulation to multi-level poll and response using character- or bit-oriented protocols. Available in single- or dual-disk versions, the Comtest 200 comes with an integral five-inch CRT screen and a video output for driving an external CRT.

The companion Comtest 100 is a passive, non-interactive data analyzer that allows the operator to observe network traffic without interrupting normal communications. Synchronous and asynchronous data can be monitored and recorded at bit rates to 19.2 kb/s and in a variety of code sets and protocols. The Comtest 200 is priced at $9,950, and the Comtest 100 at $4,600.
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Author:Edwards, Morris
Publication:Communications News
Article Type:evaluation
Date:Nov 1, 1985
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