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|   8 E1 Echo Canceller with VQE   |

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Product Overview

Comarra offers the industry's most compact 8 x E1 voice quality enhancement (VQE) and echo canceller solution in a 19-inch, 1U (44mm height) chassis, with echo tail-displacement feature (echo tail off-set) feature which is user programmable from 0ms. to 896 ms. Echo cancellation on each channel is 128 ms. bidirectional (near-end and far-end) echo cancellation. The 8 x E1 VQE and echo canceller solution offers a unique, user definable echo-tail displacement feature which may be programmed by the user, between 0ms. to 896ms. on the return path to cancel echo-tails, both at the near-end and the far-end, in the most demanding network conditions.

Comarra offers echo cancellation and voice quality enhancement solutions for the following network situations:

  • Wireline
  • International Gateway
  • Wireless
  • Satellite
  • IP Gateway
The echo canceller solutions are also ideal for long distance telephony, GSM, CDMA, TDMA, VoIP, satellite and radio communication applications.

The echo canceller equipment is compliant to ITU-T G.164, G.165, G.168 (2000/2002) requirements for echo cancellation. The echo canceller solutions offers carrier-grade voice quality per AT&T Voice Quality Assessment Lab. Echo cancellation on each channel is 128ms. Bi-Directional with user definable echo-tail displacement between 0ms. to 512ms.

Key Highlights of the Comarra E1 Echo Canceller solution

  • Comarra offers the industry’s most compact 8 x voice quality enhancement (VQE) & E1 echo cancellers solution. 8 E1 (or T1) echo cancellers in a 1U (44mm) high chassis – industry’s smallest footprint.

  • 128 ms. bi-directional (near-end and far-end) echo cancellation with echo-tail displacement (tail-offset) from 0ms.to 896ms.

  • Programmable echo-tail displacement (echo tail off-set) from 0ms.to 896ms.

  • Echo-Tail Displacement allows user to programmed lay off-set on return path and user can cancel near-end and far-end echo from single installation.

  • Ideally suited for GSM Networks to eliminate "back ground noise" to enable GSM Networks to function at half-rate (HR) (with full-rate voice quality) there by doubling spectrum usage in GSM networks.

  • Echo Cancellation on each channel is 128ms.bi-directional (near-end and far-end).

  • Compliant to ITU-TG.164,G.165,G.168 (2000 / 2002) recommendations.

  • Electrical Echo-Cancellation resulting from networks delays and delays arising due to complex voice compression algorithms in hybrid PSTN and long distance networks.

  • Acoustic Echo-Cancellation required for mobile networks for cancelling echo-tails that originate form cellular hand-sets, designed with poorly designed acoustic feedback.

  • Auto Voice Level Control and VQE (Voice Quality Enhancement features) required for reducing background noise from calls originating from crowded public places or other noisy environments and maintaining a uniform Voice level in a Network. Improves voice quality.

  • User programmable dedicated data channels.

  • Remote access through Telnet.

  • 8 xE1 (or T1) VQE and echo cancellers ina1U (44mm) high chassis- industry’s smallest footprint.

  • R2, CAS, PRI ISDN (30B+D), C5, CCS, Q50 (AB/CD), C7, SS7

  • User Programmable signaling options

  • Cancels near-end and far-end echo from single installation

  • CCS, Q50 (AB/CD)

  • Applications include wireline, wireless, satellite, international / long distance gateways, DCME and radio communication networks

  • Usable in telecommunications systems worldwide

Type of VQE and E1 Echo Canceller offered
8 E1 Echo Cancellers per 19 inch, 1U (44mm) chassis

8 x Voice Quality Enhancement (VQE) E1 echo canceller 19inch, 1U (44mm) chassis, 128ms. bi-directional echo cancellation tail. E1 Inputs and Outputs are balanced 120 Ohms, RJ-45.

Question. What is tail-displacement?

Answer Echo tail-displacement (echo tail off-set) is an important feature used in bi-directional echo-cancellation, to make it effective and useful for bi-directional echo-cancellation.

Explanation Bi-directional (defined as near-end and far-end automatic echo cancellation operation) echo-cancellers have the capability of cancelling echoes in BOTH directions (on the Transmit as well as the Receive paths), by installing them at a single location. Bi-directional echo-cancellers can be installed at a single location, either the Near-End or the Far-End, and used to cancel BOTH Near-End and Far-End echo-tails, from a single installation.

Usually, satellite links and intercontinental VoIP circuits have fixed network delays which exceed the capabilities of commonly available (192ms) echo-cancellers for bi-directional echo-cancellation, thus making them unsuitable for bi-directional echo-cancellation.

Example An inter-continental satellite or a VoIP link may have a fixed end-to-end round-trip delay of 300ms, thereby rendering all commonly available echo-cancellers, with even 192ms echo-cancellation capabilities, in-effective for bi-directional echo-cancellation.

Using the Echo Tail-Displacement (echo tail off-set) feature, the User may offset and account for the fixed round-trip network delay on the return path so that the echo-cancellation window on the return-path is shifted by 300ms., so as to allow the bi-directional echo-canceller to function effectively in BOTH directions and to cancel BOTH Near-End, as well as the Far-End echo-tails on the return path, even if the echo-canceller is installed at the Near-End in a given network.

Echo Tail-displacement allows the user to program a delay off-set on the return path, so that the User may cancel both near-end and far-end echo-tail with a single Echo Canceller installation. The echo tail-displacement allows the user to compensate for the fixed network delays on the return path of the echo-tail, so that the user can effectively cancel, both near-end and far-end echoes using a single Echo Canceller without being limited by the fixed end-to-end delay of that network link.

Comarra's Echo-Canceller has a user programmable "echo tail-end displacement" (echo tail off-set) from 0ms. to 512ms.

This feature allows the use of a single Echo Canceller installation to cancel echo-tails in both directions over inter-continental satellite or VoIP links where the fixed network delays are excessive (beyond and in excess of (example) 192ms. echo-cancellation capability of the most commonly sold bi-directional Echo Canceller solutions).

Question:  My Network has a total of 300ms. end-to-end delay. How can I use a 128ms. bi-directional echo canceller to cancel, both, near-end and far-end echoes?

Answer:  The use of the "programmable echo tail-displacement" feature in our Echo Cancellers allow the user to cancel echoes on the return path even if the network delays exceed 128ms.

The fixed network delay shall be calculated ascertained and programmed as the "echo tail-displacement" on the return path. This shall allow the user to use a single Echo Canceller to cancel echoes, bi-directionally, even if the total network end-to end delay is in excess of 300ms.

The Comarra 128ms., bi-directional Echo Canceller solution, equipped with a user programmable "echo tail-displacement" feature is superior than a simple single 192ms. bi-directional Echo Canceller solution for cancelling both near-end and far-end echoes, even if the fixed round-trip network delays exceed 300ms (please see the example above).

E1 Echo Canceller - Highlights

Provides voice echo cancellation of up to 128ms Bi-Directional for 8 E1 Echo Cancellers

  • Meets ITU-T G.164, G.165, G.168 (2000 / 2002) requirements for echo cancellation

  • Custom user definable echo-tail displacement between 0ms. to 512ms. This allows the user to cancel echo in both directions (near-end and far end), even in most difficult conditions i.e. excessive transmission delays that are common on VoIP networks and satellite links.

  • Voice Quality Enhancement:

    • Removes background noise

    • Automatic level control (maintains VF levels)

    • Acoustic Echo Control

    • Adaptive listener Enhancement

  • Signaling protocols supported:

  • 30B+D PRI ISDN (Euro ISDN) signaling,

  • 31B (31 voice channels) with out-of-band signaling,

  • R2 CAS Signaling,

  • SS7 signaling (on any user selected time-slot).

  • C5, CCS, Q50 (AB/CD)

  • All signaling options are User Selectable / User Programmable.

  • Allows digital data transmission on user-selected time-slots.

  • E1 link by-pass on power failure. This feature helps to maintain the link integrity even in the event of power failure

  • The echo canceller supports fax / modem G.164 and G.165 (2100 Hz) tone disable.

  • User selected clock / synchronization option - Internal, External and Loop-Timed clock

  • Stratum 3e clock for stable Internal clock / holdover clock in the event of failure of any of the selected clock sources

  • Remote access through telnet over LAN / TCP-IP link (10/100BaseT)

  • Local access through COM port (RS232 serial port)

  • Easy to use text based CLI commands for management and configuration

  • Adjustable gain/loss settings on all channels. Provides the user the flexibility to adjust and optimize the voice,  transmit and receive levels.

  • Non-Linear Processor with Comfort Noise Insertion

  • Option for user to select voice echo cancellation or digital-data transmission selectively on each time-slot for selective echo cancellation. This feature allows the user to use selected time-slots for data transmission to enable digital data / CCS signaling transmission.

  • Transmission (data mode), while keeping the echo cancellation "ON" on the remaining time-slots (voice mode), on which echo is required to be cancelled.

  • Ensure echo canceller maintains excellent performance at all times in presence of tones or signals including DTMF tones.

  • Fully independent 8 E1 (or T1) echo canceller

Unique E1 Echo Canceller Feature:

USER PROGRAMMABLE TAIL DISPLACEMENT: User definable echo-tail displacement is selectable between 0ms. to 896 ms. on the return-path. This feature allows the user to cancel echo-tails in BOTH directions (both near-end and far-end echo tails), even in most demanding conditions that are common on VoIP networks and satellite links.

USER PROGRAMMABLE SIGNALING OPTION: The E1 echo cancellers supports the following signaling protocols: Signaling protocols supported: 30B+D PRI ISDN (Euro ISDN) signaling, 31B (31 voice channels) with out-of-band signaling, R2 CAS Signaling, SS7 / C7 signaling (on any user selected time-slot), C5, CCS, Q50 (AB/CD). All signaling options are User Selectable / User Programmable. Allows digital data transmission on user-selected time-slots.

USER PROGRAMMABLE DEDICATED DATA CHANNELS: The User my specify / define the dedicated data channels so that they are ALWAYS and COMPLETELY BYPASSED from the echo-cancellation circuitry - leaving those specifically assigned dedicated time-slots for digital data transmission (including video transmission).

The E1 echo canceller supports 2100 Hz fax / analog data modem tone detection and echo canceller disabling on all channels.

Signaling Support:

The E1 echo cancellers supports the following signaling protocols: Signaling protocols supported:

  • 30B+D PRI ISDN (Euro ISDN) signaling
  • 31B (31 voice channels) with out-of-band signaling
  • R2 CAS Signaling
  • SS7 signaling (on any user selected time-slot)
  • C5, CCS, Q50 (AB/CD)
  • All signaling options are User Selectable / User Programmable
  • Allows digital data transmission on user-selected time-slots.

Voice Quality

  • Acoustic Echo Control (AEC)
  • Adaptive Noise Reduction (ANR)
  • Automatic Level Control (ALC)
  • Adaptive Listner Enhancement (ALE)

Fault Recovery:

The echo canceller equipment offers fault recovery feature. It offers automatic by-pass upon power-supply failure (i.e. it offers E1 circuit by-pass in the event of power supply failure).

Remote Monitoring and Control

  • Remote access through telnet over LAN / TCP-IP link (10/100BaseT)

  • Local access through COM port (RS232 serial port)

Applications for the E1 Echo Cancellers

  • Wireless: GSM, CDMA, TDMA, PCS and Cellular Base Stations.

  • Digital Circuit Multiplication Equipment (DCME) : Satellite Communications and Multiplexers.

  • PCS, cellular, mobile, and digital cordless wireless systems.

  • PBX and central office systems.

  • Datacomm: Voice Over Frame Relay, Voice Over ATM, and Voice Over Internet.

  • Voice over ATM, Frame Relay or packet switching systems and fax transmissions.

  • Central Office and PBX: Network Trunks, Echo Canceller Pool, Common Equipment and Audio Conferencing Bridges.

  • Voice over datacomm including voice over Internet (VoIP), voice over ATM (VoATM) and voice over Frame Relay (VoFR).

Datacomm Applications

  • Voice Over Frame Relay

  • Voice Over ATM

  • Voice Over Internet / LAN

Central Office and PBX Applications

  • Network Trunks

  • Echo Canceller Pool

  • Common Equipment

  • Audio Conferencing Bridges

Voice Over ATM Applications

  • A multi-channel echo canceller resource or pool is shared among many channels to reduce cost

  • Echo cancellation is done at a DS0 level

Satellite Communications Applications

  • Digital Circuit Multiplication Equipment (DCME)

Wireless Applications


  • Digital Cordless and Cellular Basestations

Voice Over Frame Relay, ATM Applications

  • Frame Relay and ATM routers and switches introduce large, variable, and unpredictable delays.

  • Echoes from the Public Switched Telephone Network (PSTN) in combination with the delays from Frame Relay and ATM equipment yield objectionable speech quality.

Application Diagrams for the E1 Voice Echo Cancellers

  • Application Diagram - 128ms Bi-directional E1 Echo cancellers

Others Links:

  STM SDH Multiplexers
  E1 VoIP-GSM Gateways
  VoIP SS7 and C7 Solution
  Echo Cancellers and VQE Solutions
  GSM Gateways / GSM Channel Banks
  E1 and T1 over Ethernet (TDM over IP)
  Digital Access Cross Connect Switch (DACS)
  E1, T1, E3, DS3, Ethernet Converter (IP over TDM)

Technical specifications are subject to change without notice.
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