Category

Symptom

Possible Cause and Solution

Signal tone detection faults

Case 1: The busy tone cannot be detected.

The cause is that signal tone detection parameter settings do not match those at the carrier side. You are advised to modify signal tone detection parameters, or automatically detect and obtain signal tone parameter settings at the carrier side by referring to Common AT0 Parameter Reference.

Case 2: Busy tone misdetection occurs.

The system provides various built-in busy and congestion tones except the standard busy tone. If the local ringback tone or other signal tones use the same frequency and cadence as a built-in busy tone or congestion tone, busy tone misdetection may occur. In this case, capture call logs (which must be enabled for the RM and AT0 modules). Search for information similar to "[Rm.c 17936]usToneID=7, VoiceToneID=2" in call logs. The options for usToneID are as follows:

ϒ⁄0: ringback tone

ϒ⁄1: busy tone

ϒ⁄2: dial tone

ϒ⁄3: congestion tone

ϒ⁄4: unallocated number tone

ϒ⁄5: howler tone

ϒ⁄6: busy tone 2

ϒ⁄7: busy tone 3

ϒ⁄8: busy tone 4

ϒ⁄9: busy tone 5

ϒ⁄10: busy tone 6

ϒ⁄11: congestion tone 2

ϒ⁄12: congestion tone 3

ϒ⁄13: congestion tone 4

ϒ⁄14: congestion tone 5

In "[Rm.c 17936]usToneID=7, VoiceToneID=2", the value of usToneID is 7 that corresponds to busy tone 3. As a result, busy tone 3 is detected and treated as the busy tone incorrectly. You can modify or delete the frequency, cadence, or detection period setting for busy tone 3 to avoid busy tone misdetection.

Voice quality fault

Case 1: Noise exists in calls.

The AT0 is easily affected by environmental factors, and noise is generated. You can perform the following operations to reduce noise:

ϒ⁄Set the impedance to that at the carrier side.

ϒ⁄Ensure that the device is grounded properly. (You can check the grounding status by checking noises of FXO and FXS ports. For details, see Obtaining AT0 Interface Parameters.)

ϒ⁄Enable HPF for FXO ports.

ϒ⁄Disable the comfort noise generation (CNG) function provided by the EC.

Case 2: Echoes exist in calls.

The AT0 is easily to generate electrical echoes due to impedance mismatch. You can perform the following operations to cancel echoes:

ϒ⁄Set the impedance to that at the carrier side.

Case 3: Voice shearing occurs during double-talk.

When the NLP is enabled for canceling echoes, the NLP will cancel signal tones whose volume is lower than Volume.Rin+ERL. If the volume difference is large between the two parties on a call, the system may consider voice whose volume is lower than Volume.Rin+ERL as echoes and cancel the voice. You can adjust EC return loss (erlsel) and Local signal threshold (ecsinener) properly to rectify this fault.

CLIP fault

The calling number for an incoming call through the AT0 trunk is not displayed.

The possible causes are listed below: (You are advised to directly connect a POTS phone with the CLIP function to an FXS port in the upper-level office to locate the cause.)

ϒ⁄The CLIP function is disabled at the carrier side.

ϒ⁄The CLIP mode (FSK/DTMF) is inconsistent with that at the carrier side.

ϒ⁄The CLIP time is inconsistent with that at the carrier side.

ϒ⁄The on-hook gain is too high or low to detect FSK energy.

Call volume fault

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To rectify the fault that the call volume is too high or low, perform the following operations:

ϒ⁄Adjust the send and receive gains of FXO ports on the OSU board. (If the receive gain is too low, DTMF signals may not be detected during two-stage dialing.)

Failure to detect DTMF signals during two-stage dialing

Two-stage digit collection fails.

The possible causes and solutions are as follows:

ϒ⁄The energy of DTMF signals is too low when the DTMF signals reach FXO ports.

ϒ⁄Echo or noise interference exists.

Rectify the fault by canceling echoes or noise.