Determining Best Match Impedance on Analog Voice Ports in Cisco IOS Router

A.

THL tone sweep allows all available impedances for a single test call to a quiet termination point out to the PSTN.

You do not need to manually disable ECAN on the voice port under test.

The test feature switches impedances automatically for the tester.

The test feature calculates the arithmetic mean ERL and reports the mean for each channel profile at each impedance setting.

Then, at the end of the test, the feature specifies the best match impedance setting.

This test requires minimal supervision.

References: http://www.cisco.com/c/en/us/support/docs/voice/ip-telephony-voice-over-ip-voip/64282-impedance-choice.html.

The correct answer is D. inject-tone local sweep.

Analog voice ports on Cisco IOS routers require the correct impedance setting for optimal voice quality. The correct impedance setting is dependent on the connected device, such as a fax machine, modem, or telephone. The process of determining the correct impedance is called impedance matching.

Traditionally, administrators would determine the best match impedance by shutting down and then no shutting the analog voice port, which would trigger a tone sweep test. This process is time-consuming and disruptive.

However, with the inject-tone local sweep method, administrators can determine the best match impedance without having to shut down and no shut the ports. This method injects a tone sweep signal onto the analog voice port while the port is in use. The signal reflects back from the connected device, and the router measures the reflection to determine the best match impedance.

To perform an inject-tone local sweep, follow these steps:

1. Connect the device to the analog voice port.
2. Enter the following command in global configuration mode:

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Router(config)# voice-port slot/port 

Replace "slot" and "port" with the appropriate values for the analog voice port.

3. Enter the following command:

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Router(config-voiceport)# input gain -3 

This command sets the input gain to -3 dB. This value is appropriate for most devices.

4. Enter the following command:

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Router(config-voiceport)# output attenuation 6 

This command sets the output attenuation to 6 dB. This value is appropriate for most devices.

5. Enter the following command:

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Router(config-voiceport)# inject-tone local sweep 

This command injects the tone sweep signal onto the analog voice port.

6. Observe the output to determine the best match impedance.

The inject-tone local sweep method is faster and less disruptive than the traditional shut down and no shut method, making it the preferred method for determining the best match impedance on analog voice ports in Cisco IOS routers.