Specifications

AN93
198 Rev. 0.9
Poor Audio Recordings
If an audio recording is not done correctly, it will not help debug the communication protocol. The following are
some examples of how things can go wrong in the process. The technical issues are not difficult, but, many times,
these recordings are made in the field where there may not be the knowledge to do this correctly. To get good data
from the field, customers or support people need to be shown the correct method.
Figure 62. Recording Made at Excessive Level
The above recording was made at an excessively high level. One can see clipping in the time domain and
numerous distortion products in the frequency domain.
Figure 63. Recording Made with AGC “Noise Reduction”
The above recording was made with AGC "Noise Reduction" still enabled, as you can see from the gradual level
drop in the time domain graph at the start of V.22 negotiations. It also shows evidence of a microphone being used
instead of a Radio Shack adaptor. This is visible in the frequency domain graph due to the horizontal striations (an
undulating frequency response) during the scrambled portion of the V.22 communication. One can also see third
harmonic distortion.