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Cisco Digital Gateway DT-24+

Field Notice: Audio Levels and Echo on Cisco Access Digital Gateway


January 10, 2000



Products Affected

Cisco Access Gateways DT-24+ and DE-30+

Problem Description

When using a DT-24+ or DE-30+, callers on the Public Switched Telephone Network (PSTN) side of the connection may sometimes hear an echo.

Background

Possible causes of the echo are:

  • The transmit level (outbound) audio from the gateway is too high (hot).

  • The receive level (inbound) audio from the PSTN is too high (hot).

A feature has been added to CallManager 2.4(b) that allow users to adjust the audio levels (pad settings) to eliminate the echo problem, if the problem is on the PSTN side.

Problem Symptoms

The problem occurs when callers on the PSTN side of the connection hear an echo. This can be corrected by adjusting the gateway audio levels.

If callers are experiencing echo only when connected to a particular central office or PBX, the central office needs to make the appropriate adustments to the audio levels on the ISDN PRI.

Workaround/Solution

Note:?If the problem is not on the PSTN side of the connection, do not change the default pad settings on the Cisco Access Digital Gateway DT-24+/DE-30+.

Cisco recommends using a telecom test set on the PRI to verify that the audio levels are indeed out of telco specifications, then add or gain or loss accordingly. If the appropriate test gear is not available, or if you are unfamiliar with the test gear, try different pad settings and make test calls until the echo is reduced to an acceptable level on the PSTN caller side.

The software required to adjust the audio levels on the DT-24+/DE-30+ is listed below:

  • Cisco CallManager release 2.3 or 2.4(b)

  • Cisco Digital Access load file D003G024.bin

  • Cisco DickTracy utility ( The DickTracy Utility is used to adjust the audio levels on the DT-24+/DE-30+. It is an internally developed utility that is used to adjust audio levels in the GW loads. It is embedded in CallManager.)

Default pad settings for the D003G024 load are listed below:

TX RX
DE-30+ -6db -4db
DT-24+ 0db 0db 

Note:?The D003G024.bin gateway load and DickTracy utility are part of the 2.4(b) load but are not the default (see steps 2, 3, 4 below). For the 2.3 load, follow steps 1 - 4 below.

Follow the steps below:

  1. If you are working with a Cisco CallManager release prior to 2.4(2b), copy the gateway load file D003G024.bin to the Cisco\TFTPPath folder.

  2. Using Cisco CallManager Administration, set the Load ID to D003G024 for the Cisco Access Digital Gateway DT-24+/DE-30+ in question. Then click Reset.

  3. Allow the gateway time to re-register with Cisco CallManager, then use the Microsoft Performance Monitor verify that the gateway has registered.

  4. If the DickTracy utility is not already installed on the server where Cisco CallManager is running, copy the file DickTracy.exe from Cisco CallManager release 2.4(2b) to any location on the hard disk of the server.

  5. Run the DickTracy utility.

  6. In the DickTracy window that displays, select "Connect" from the File menu.

  7. Enter the IP address of the Cisco Access Digital Gateway DT-24+/DE-30+, and always use TCP port 2005. Then click OK.

  8. Select "Send Cmd" from the Options menu to open the DickTracy command window. It may take 15 to 30 seconds for the gateway to respond and for the command window to open.

  9. In the DickTracy command window, enter 3 for the Task ID. Then enter other commands as needed.

    The command line syntax is as follows:

    • show pads - Display current settings.

    • set txpad[32] NN - Sets transmit pad value. (Brackets are required.)

    • set rxpad[32] NN - Sets receive pad value. (Brackets are required.)

    • set nvram - Burns values to NVRAM. (Required to save the new settings.)

    Where:

    ? [32] specifies all B-channels. You can also specify individual channel numbers, such as [01] for channel 1, [02] for channel 2, and so forth.

    ? NN is a positive number between 00 and 63 that specifies the audio level, with 32 equal to zero dB, as below:

    NN Pad value
    00 mute
    01 -31dB
    02 -30dB
    03 -29dB
    04 -28dB
    . .
    . .
    . . 
    29 -3dB
    30 -2dB
    31 -1dB
    32 0dB
    33 +1dB
    34 +2dB
    35 +3dB
    . .
    . .
    . .
    62 +30dB
    63 +31dB 
    
    

New pad settings take effect on the next call made on each B-channel. Calls in progress are not affected by setting changes.

CallManager Software and Documentation

DDTS

To follow the bug ID link below and see detailed bug information, you must be a registered user and you must be logged in.

DDTS

Description

CSCdp55084

The only remaining problems are echo, which is experienced when calling from a PSTN/Mobile phone to an IP phone. Most of the echo occurs when using mobile phones to dial in to the IP telephony environment. But it can also occur with fixed telephony. Signal fading is an issue as well.

Engineering Response: This issue is a result not of the phone itself, but of the signal from the Central Office. The digital access gateway software was modified to allow setting attenuation values for the ingress and egress signals. This change allows the user to adjust signal strengths, and the issue has been resolved using this mechanism.

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods: