Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 288)

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288 Rev. 1.3
Examples of Line Impairments
DTMF Distorted by Low Line Level
Figure 71. Defective DTMF
Figure 72. Normal DTMF
Solutions:
 Fix the telephone line.
 Lower the DTMF level with AT:U46, 0BD0 or AT:U46, 0CF0
 Check the loop-current level with AT:R79 and AT:R6C.