Crocus Inverse Multiplexer

  • Connects up to 8 Mbps serial data over several E1 links
  • Automatic speed adaption in case of E1 link loss
  • Advanced free maintenance software
  • Manageable under HP OpenView«
  • Modular plug-in DTE interfaces for maximum flexibility
  • and efficient stock management


The Crocus Inverse Multiplexer provides transparent transmission of synchronous data at speeds up to 7808 kbps on a serial interface using multiple 2 Mbps E1 lines. The equipment enables one to cross the 2 Mbps barrier without having to adapt the installed user applications, which can be operated at their fastest rates.

The system is based on an extension of recommendation ISO/IEC 13871 (1995), which offers an efficient bonding mechanism for multiple E1 lines. These E1 lines may have a difference in throughput delay as high as 64 msec so different routings of the constituent E1 lines can be used. In addition, an automatic fallback step-up mechanism permits the user to add or suppress E1 lines and so to adapt dynamically the user speed in multiples of 1952 kbps.

A complete range of serial plug-in interface boards makes the Crocus Inverse Multiplexer ideal for interfacing with almost any high-speed application. Traditional interfaces such as V.35, V.36, X.21 or RS-530 and also direct 10BaseT connections with integrated bridge functionality are available. All these interface boards can be exchanged in only a few seconds.

Typical topologies include high-speed serial data interconnectivity for direct point-to-point connections and also data services in combination with E1 Networks, like DACCS (Digital Access Cross Connect Systems) or SDH (Synchronous Digital Hierarchy) backbones. If the equipment is used in combination with HDSL modem technology (e.g. Crocus HDSL), the existing local loop copper infrastructure can be used for this high-speed data service. In the example below, a user application (router) is connected with a high-speed serial connection (V.36, 7808 kbps) to a Crocus Inverse Multiplexer. The Crocus Inverse Multiplexer E1 lines are connected to 4 HDSL links, which use regular twisted copper pairs for making the connection to a Digital Access Cross Connect System (DACCS). The DACCS will route the E1 lines to an access point of a frame/relay backbone, where the different E1 lines are regrouped by another Crocus Inverse Multiplexer before the user data enter the frame/relay backbone infrastructure.


Typical Application: High speed access to a packet switched backbone through a DACS

The equipment is shipped with a unique and free Windows application, which gives the user a powerful maintenance tool for both the local and the remote equipment. It provides not only for configuration of the equipment but also for an interactive picture, status interrogation, real-time performance monitoring, and statistics retrieval.

In addition, the Crocus Inverse Multiplexer has an Ethernet connection, which allows for SNMP management. Management modules are available for different integrated management platforms, like HP OpenView«. On those platforms, one can combine the management of the Crocus Inverse Multiplexer equipment with the management, for example, of modem and router


Inverse Multiplexing

Number of E1 links up to 4
Maximum delay variance between links 64 msec
Throughput delay 50 Ásec + variance between links
Framing overhead 1.6 %
Net user speed per E1 link 1952 kbps
Performance Monitoring per E1 link End-to-end CRC-4

E1 Link interfaces

Applicable standards ITU-T G.703, G.704, G.732
Jitter performance ITU-T G.823
Nominal line data rate 2048 kbps
Line code HDB3
Line connection 120 ohm balanced, RJ45 connector
75 ohm unbalance, BNC coaxial connectors
Performance Monitoring G.703 CRC-4 (configurable)

Station clock interface

Nominal rate 2048 kbps
Line code HDB3
Line connection 120 ohm balanced, RJ45 connector
75 ohm unbalance, BNC coaxial connectors

Ethernet LAN Interface (management)

Connector RJ45
Operation 10BaseT Ethernet

Console Port

Connector 9-pins subD Female V.24/RS-232
Data Rate 9600 bps, asynchronous, 8N1

Clocking Schemes

External transmit clock (station clock)
Transmit clock slaved on E1 receive clock with possibility for automatic E1 channel source selection
Internal transmit clock

High-speed data interface

Clocking Speed
1952, 3904, 5856, 7808 kbps, following the number of E1 links used
Automatic fallback to next lower rate in case of E1 link failure

Serial interfaces available:

V.35 ISO 2593 (female 1,6mm pin)
V.36 ISO 4902 (DB37 female)
X.21 ISO 4903 (DB15 female)
RS-530 ISO 2110 (DB25 female)
Bridge 10BaseT (RJ45)
Conform IEEE 802.3
Integrated Bridge functionality

Front panel Indicators

General PWR



Test Indicator

Ethernet LNK




Link Integrity

Data Collision

Transmit Data

Receive Data

For each E1 LOS




Loss Of Signal

Loss Of Frame synchronisation

Alarm Indication Signal

CRC-4 performance problem



Transmit Data (circuit 103)

Receive Data (circuit 104)


Local Analog Loopback (Loop3) for each individual E1 line

Local Line Loopback (Loop4) for each individual E1 line

Local Digital loop (Loop2) for high-speed user interface

Remote digital loop (remote Loop2) for high-speed user interface

Integrated BER testing conform ITU-T O.151 (215-1 pattern)

Mechanical data

Desktop version H x W x D: 50 x 430 x 270 mm weight: 4.3 kg
Rack-mount version H x W x D: 43 x 482 x 270 mm weight: 4.6 kg

Environmental Requirements

Ambient operational temperature

Storage temperature

Maximum altitude

Relative humidity


0░ C to 50░ C

-25░ C to +70░ C

3000 m

0% to 95% non-condensing

Power Requirements

Power voltage 90-264 Vac, 47-63 Hz 20-70 Vdc
Maximum power consumption 25 W

The Crocus Inverse Multiplexer

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