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Larscom Mega-T / Mega-E Inverse Mux

Mega-T - combine from 2 to 4 T1s into a high-speed data channel which is completely transparent to your application. Inverse-multiplexing technique lets you use standard T1 facilities for the greater-than-T1 rates. Mega-T supports virtually any dedicated channel application using a HSSI (High-Speed Serial Interface) or EIA530 (V.35/RS449) interface. The total bandwidth for the application can be any multiple of 1.344 or 1.528 Mbps, up to 6.112 Mbps.


  • Economical access to
    greater than - T1 bandwidth for high-speed applications

  • Direct connection to V.35- and
    HSSI-compatible equipment

  • Complete visibility of T1 and DTE
    channel performance

  • Rapid trouble notification, isolation, and recovery

  • Integral SNMP agent

  • 125 milliseconds differential delay

  • Adaptability to changing standards and services, including
    downloadable software


Multiple T1 Inverse Multiplexer

In the 1980s, most corporate networks employed T1 backbones. Today, many network managers find they need greater-than-T1 bandwidth for new high-speed applications. Often, however, a DS3 circuit is either unavailable or cost prohibitive. ® The Mega-T Multiple T1 Inverse Multiplexer bridges the gap between T1 and T3. Inverse-multiplexing up to four T1 lines, Mega-T creates a single logical data channel which is the sum of the T1 bandwidths. On the DTE side, Mega-T provides an EIA530 (V.35/RS449) or HSSI port operating at data rates up to 6.112 Mbps. On the network side, T1 interfaces support all standard framing and coding formats, and include optional built-in CSUs. Mega-T includes advanced monitoring and alarm functions to help you maintain your critical communication channels. And built-in diagnostics ensure that you can isolate problems quickly and accurately. To help you adapt to changing standards and service offerings, Mega-T lets you download software upgrades from a standard PC . . . without hardware replacement or downtime.


Typical Mega-T Application

  • Mega-T employs inverse multiplexing

  • to create a high-speed data channel.

  • Here, Mega-T uses four T1 lines to

  • create a 6.112 Mbps channel for a

  • LAN internetworking application.


LAN/WAN interconnection

Economical High-Speed Data Channels

Mega-T’s unique inverse-multiplexing technique lets you use standard T1 facilities for the greater-than-T1 rates that many of today’s internetworking applications require. Using Mega-T, you can combine from 2 to 4 T1s into a high-speed data channel which is completely transparent to your application. Mega-T supports virtually any dedicated channel application using a HSSI (High-Speed Serial Interface) or EIA530 (V.35/RS449) interface. The total bandwidth for the application can  be any multiple of 1.344 or 1.528 Mbps, up to 6.112 Mbps. Mega-T network interfaces feature integral T1 CSUs, which are required for connection to public T1 networks. Or you can order basic DSX-1 interfaces for connection to private T1 facilities . . . or any other application where CSUs are not required. D4/ESF framing options (including the ANSI T1.403 standard for ES F) and AMI/B8ZS coding options ensure that Mega-T is compatible with all T1 services.

Performance Monitoring and Diagnostics

To keep you apprised of your network’s performance, Mega-T exceeds the monitoring requirements specified in AT&T Pub 54016—in D4 mode as well as in ESF. Numerous 24-hour registers provide complete performance pictures of the individual T1s and the composite data channels. To help you isolate and diagnose problems, Mega-T offers several loop-back options for the T1 and DTE channels, plus a self-test.

Automatic Rate Fallback and
Disaster Recovery

In this example, pairs of T1s are routed through different inter-exchange carriers (IECs) for additional reliability; routing T1s through different IECs decreases the likelihood of all T1s failing at the same time. Normally, the data channel is 6.112 Mbps using all four T1s. If one or more T1s fail, Mega-T can automatically fall back to the rate provided by the remaining T1s—then automatically restore the failed T1s when they return to required performance levels.


Disaster recovery and backup

Automatic Rate Fallback and Recovery

To ensure that your communication link stays available when individual T1s fail, Mega-T can automatically fall back to a lower data rate if a T1 line does not meet the performance requirements you specify. And Mega-T can automatically restore a dropped T1 line when performance again meets your requirements. If you create your high-speed channel using different routes and/or carriers, you can greatly reduce the risk of a complete channel failure. Should major problems take down one route or carrier, the T1s using another route will ensure that your communication channel stays open.

T1 and T3 Access Options

Mega-T can access the public network directly via T1 access lines, or through an M13 multiplexer and a T3 access line.

Broadcast-quality video

Centralized Management

You can manage Mega-T from an SNMP Network Manager through a standard RS232 SLIP interface. Mega-T’s integral SNMP agent supports the standard DS1 MIB and all defined Mega-T alarms. In applications where Mega-T is used in conjunction with Larscom’s Orion 4000 Broadband Access Multiplexer, Mega-T may also be managed from the Orion 4000 shelf, thereby simplifying management of the entire system. You can also manage Mega-T using standard ASCII terminals. Two RS232 ports allow local and remote connections, including automatic alarm dial-out. The easy-to-use interface features menus and pop-up windows. A menu-driven LCD interface on the Mega-T front panel allows local configuration and control of most Mega-T functions.


T1 Interfaces  
Interfaces 2 or 4 T1 ports; 1.544 Mbps ±50 bps; electrical per AT&T Pub 62411
Line Codes Bipolar Return to Zero: Alternate Mark Inversion (AMI) or B8ZS
Framing Options ESF (per AT&T Pub 54016, Issue 2, and ANSI T1.403) or D4
Surge Protection 1000 V pulse per AT&T Pub 43601; cross-voltage protection per UL 1459 (Issue 2)
Connectors Four DA15; adapters for RJ48 and wire-wrap (up to 655 feet for DSX-1)

DTE Data Port
Interface Type High Speed Serial Interface (HSSI), differential ECL, SCSI-II 50-pin, female;
  CCITT V.35 (V.10/V.11) and/or RS449; DB25 female connector (EIA530);
  adapters for MS34 (V.35) and DC37 (RS449)
Data Rate Any multiple of 1.344 (when bit 7 stuffing is employed) or 1.528 Mbps,
  up to 2.688/3.056 Mbps (2 T1s) or 5.376/6.112 Mbps (4 T1s)
Station Clock Input TTL levels; 50 ohms impedance; BNC connector

Inverse Multiplexing
DS1 Alignment Algorithm 1 to 4 DS1s, user-mapped in any pattern (U.S. patent 5251210)
Idle Pattern All ONES on DTE port loss
T1 Differential Delay Up to 125 milliseconds

Management Interfaces
Front Panel Menu-driven: 80-character LCD, 8 entry keys, 4 LED status indicators
Local/Remote Port Two RS232 ASCII, to 9600 baud; DE-9 (EIA574) male connectors
SNMP Connection via SLIP; integral agent per RFC 1406

Monitoring & Diagnostics
Performance Registers Per AT&T Pub 54016 (Iss. 2), plus additional 24-hour registers for logical channel
Alarms Automatic dial-out on user-specified alarms (Hayes-compatible dialer);
  automatic rate fallback on selected alarms; optional automatic restoral
Loopbacks Per AT&T Pubs 62411 and 54016, plus local/remote DTE and logical channel loops

Power -48 V dc office battery (-43 to -53 V dc); standard 115 V ac, 50 to 60 Hz, 0.5 A max
  at -48 V, 0.5 V peak-to-peak ripple at max input current
Dimensions (H x W x D) 1.75 x 17 x 12 inches (4.4 x 43.2 x 30.5 cm); brackets for 19- or 23-inch rack
Environment 32 to 122 ° F (0 to 50 °C) ambient; up to 95% relative humidity, noncondensing
Regulatory Compliance FCC Parts 15 and 68; UL 1459 (Issue 2)




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