How to Troubleshoot Caller ID Detection Issues on FXO Port

Update Time：2017-06-19 15:47:12　Browse Times：4255　Amount Downloads：943

This document describes how to troubleshoot and resolve the Caller ID detection issues of an inbound call on FXO port of New Rock’s SIP-based VoIP gateways (MX series gateways) and IPPBX (OM series).
A Caller ID issue could be caused by several factors which could be traced from the PSTN subscriber line or from the noise on the lines.

Requirements

-  A PSTN subscriber line or analog line.
-  A regular analog phone with Caller ID display feature
-  Cool Edit pro 2.1 software (sound editing program for windows) installed on PC

Troubleshooting Steps

1.Verify if the PSTN subscriber supports Caller ID feafure (enabled)
1)Disconnect the PSTN subscriber line from the FXO port of MX or OM device and directly connect this line to an analog phone.
2)Make an incoming call (using another line or mobile phone) from the PSTN to the analog phone and check if the analog phone displays Caller ID.
3)If the Caller ID is not being shown on the phone, please contact your telco or PSTN service provider and ask them how to enable this feature.
4)If the analog phone shows the correct Caller ID on every call, please take note if the Caller ID shows before the first ring tone or after the first ring tone. (You need to configure the correct Caller ID detection mode on the web configuration of the MX or OM device.)
2.Adjust some parameters on MX or OM device
1)Make sure that the Caller ID detection feature on the device is enabled.

OM configuration page: go to Trunk > Analog trunk.

MX configuration page: go to Trunk > Feature.

2)Select the correct Caller ID detection mode on the web GUI of the MX or OM device. (you have verified this on step 1.4)

OM configuration page: go to Trunk > Analog trunk.

MX configuration page: go to Trunk > Advanced.

3)Reconnect the PSTN subscriber line to the FXO port of MX or OM device and repeat the test call.
4)If the problem is still not fixed, please perform TDM or Analog capture on FXO port of the device.

OM configuration page: go to System > TDM Capture.

MX configuration page: go to Tools > Analog Capture.

3.Analyze the captured file fxo.pcm and adjust some parameters on MX or OM device

Analyze the captured file fxo.pcm using the Cool Edit pro 2.1 software (sound editing program for windows) installed on your PC.

You can use the Cool Edit Pro to hear and analyze the Caller ID signal waveform characteristic of the captures FXO signal.
The followings show a normal caller ID signal, several abnormal caller ID signals and the corresponding solution for each abnormal signal.

Basic Analysis for a Normal Caller ID Signal

1)Take the waveform view below as an example for a normal Caller ID signal. The FSK based Caller ID signal display is very clear and can be detected.

2)Take the spectral view below as an example for a standard FSK based Caller ID signal and please take note on the duration time of the channel seizure signal. The channel seizure signal is used to signal the start of the data transmission to the CPE or TE to alert for an incoming message, and it conditions the receiver for the data. The standard seizure signal consists of 300 continuous bits (duration of 250 ms at 1200 bps) of alternating “0” (SPACE frequency) and “1” (MARK frequency).

Note:
-  New Rock devices with dspdrv version earlier than version 197 can detect a seizure signal of at least 200 continuous bits (duration of 167 ms).
-  New Rock devices with dspdrv version later than version 197 can detect a seizure signal of at least 72 continuous bits (duration of 60 ms).

3)MARK Frequency “1”. The standard FSK marking signal is composed of 180 ~ 190 bits of “1” (duration of 150 ~ 158 ms)

Note:
-  New Rock devices can detect marking signal of at least 60 bits of “1” (duration of 50 ms)

Basic Analysis for an Abnormal Caller ID Signal

1) A non-standard caller ID signal of the gain value is automatically changed.

It is observed that the Caller ID signal has a special variation of the Gain value. Using the spectrum and waveform views on Cool Edit Pro, you can see that the distribution of weak signal is the same, thus rule out the possibility of line interference.
Solution: Adjust the Gain intensity (Increase the Gain to PSTN ) and GA=6 (default is 7).  
GA Parameter name is FXO_CID_GAIN (id=341).
2)Caller ID signal is not stable.

Waveform view of the Caller ID signal: the signal’s amplitude is continuously changing.

Spectrum view of the Caller ID signal: the signal is clearer to see which frequencies are most prevalent and brighter colors represent greater amplitude components.

Solution:  Use an offline tool for analysis on Caller ID signal to determine the values for the channel SEIZURE signal and MARK signal. If it can display 3 stages of CID part without a problem, then you can use the dspdrv version later than version 197 to resolve the issue. If it cannot display, please also set parameter FXO_CID_GAIN to 6 to reduce amplitude variations.
3)There is an interference in the Caller ID signal.

Waveform view of the Caller ID signal: shows an interference in the Caller ID signal and it has a large amplitude variation at the middle portion of the signal.

Spectrum view of the Caller ID signal: the signal is clearer to see an interference that cuts-off the channel seizure signal at the middle part.

Analysis: If channel seizure signal is separated and the SEIZURE signal completed a 60ms signal time, then the Caller ID signal can still be detected on the device.
Solution: Use an offline tool for analysis on Caller ID signal to determine the values for the channel SEIZURE signal and MARK signal. If it can display 3 stages of CID part without a problem, then you can use the dspdrv version later than version 197 to resolve the issue.
4)Channel SEIZURE and MARK signals’ length or duration time are not enough.

Spectrum view of the Caller ID signal: the signal is clearer to see that the channel SEIZURE signal length or duration time is not enough and not in accordance with the national standard.

Spectrum view of the Caller ID signal: the signal is clearer to see that MARK signal length or duration time is not enough and not in accordance with the national standard.

Solution: Use an offline tool for analysis on Caller ID signal to determine the values for the channel SEIZURE signal and MARK signal. If it can display 3 stages of CID part without a problem, then you can use the dspdrv version later than version 197 to resolve the issue.
5)Caller ID signal is weak.

Waveform view of the Caller ID signal: shows that the signal intensity is weak.

Spectrum view of the Caller ID signal: the signal is weak and not clear.

Solution: Increase GA value to 11 or higher. GA Parameter name is FXO_CID_GAIN (id=341).
Adjustment range:
Less than GA9, the gain adjustment interval is 1dB
GA = 0-9 the gain value equivalent is from 0-9dB.
Greater than GA10 the gain adjustment interval is 3dB.
GA=10 the gain value equivalent is 22dB
GA=11 the gain value equivalent is 25dB
GA=12 the gain value equivalent is 28dB
6)Caller ID signal is too high.

Waveform view of the Caller ID signal: shows that the signal gain is too high.

Solution:  Reduce the GA value to decrease the signal amplitude. (for example GA=6). GA Parameter name is FXO_CID_GAIN (id=341).