TUTORIAL Obi Fading Volume - Gain Adjustment Tip

[briankelly63]

I had been having an issue with the xmit & recv switching that the Obi does during a call. This switching is a result of the half duplex and e-c-h-o reduction nature of the device. I was experiencing changing volume that would make it difficult to hear the beginning of words and sometimes random words. The problem occured on calls originated on the Obi phone port or my Asterisk trunk.
My Obi connects to my PSTN line and then to my Asterisk box. Within the line setting configuration area of the Obi you can set ChannelTxGain & ChannelRxGain. I had changed these from the defaults (0,5) to (-1,0) which at the time worked fine for me but I discovered this change indirectly affects the balance of the switching that occurs as the conversation proceeds in each direction. I also noticed that even when I wasn't having a two way conversation if I were to dial a busy signal the volume of the signal would be changing and fading in in out.
THE FIX was to put the gains back to the defaults and the problem goes away. It would seem that if the RxGain is set too low there is not enough drive within the digital switching to bias the switch toward the receiving end on something like a busy tone. I'm sure other settings will work but the key is don't go too low on the ChannelRxGain setting.

Update: If you have a fair amount of loss on your PSTN line you must increase the ChannelRxGain setting within the Line section of the Obi configuration menu. I ultimately changed mine to 8 vs. the default 5. Without this change the "half duplex" nature of call tended to be biased to me as the talker. This had the effect of muting the audio I was receiving from the distant party during syllables which made their words difficult to understand.
Update 10/14/12: I have settled on -1 for txgain and 7 for rxgain. I also found that changing the ac impedance to the one that begins with 220 made a significant difference.

Update (12-06-13):
Although previous adjustments solved most issues I had one last troublesome audio problem. If I called someone that had relatively low audio (them to me) I found that the Obi was too sensitive in biasing the audio from me to them. This issue made them sound as if they were fading in and out whenever my handset picked up even the slightest noise (breathing). My IP phones are Aastra 57i's, they do have hot audio but so do many IP phones. The solution was to turn down the 57i tx gain setting by minus ten (-10). So lesson learned is that you need to adjust gain on the Obi and your IP phone to get the proper result. If your audio is too hot going to the Obi and your just adjusting the outgoing Obi gain you may be getting the desired volume but you are over-driving the circuits in the Obi that control audio switching and e-c-h-o.

 

[Mark D. Montgomery II]

Thanks.
Based on your settings here I think I finally have my Obi sounding decent (at least testing with calling into the POTS line on my Cell).

My Current Settings:
PHONE
ChannelTXGain -2
ChannelRXGain 1

LINE
ACImpedance 220...
ChannelTXGain -1
ChannelRXGain 7

This seems to give me clear calls between my Cell and my Yealink T46G, the Unidata WPU-7800 WiFi SIP phone, and the Panasonic Analog DECT Set hooked up to the PHONE port on the Obi (I had to bump up the PHONE RXGain to make it hearable on my cell).

 

[oatmeal]

I had been having an issue with the xmit & recv switching that the Obi does during a call. This switching is a result of the half duplex and e-c-h-o reduction nature of the device. I was experiencing changing volume that would make it difficult to hear the beginning of words and sometimes random words. The problem occured on calls originated on the Obi phone port or my Asterisk trunk.
My Obi connects to my PSTN line and then to my Asterisk box. Within the line setting configuration area of the Obi you can set ChannelTxGain & ChannelRxGain. I had changed these from the defaults (0,5) to (-1,0) which at the time worked fine for me but I discovered this change indirectly affects the balance of the switching that occurs as the conversation proceeds in each direction. I also noticed that even when I wasn't having a two way conversation if I were to dial a busy signal the volume of the signal would be changing and fading in in out.
THE FIX was to put the gains back to the defaults and the problem goes away. It would seem that if the RxGain is set too low there is not enough drive within the digital switching to bias the switch toward the receiving end on something like a busy tone. I'm sure other settings will work but the key is don't go too low on the ChannelRxGain setting.

Update: If you have a fair amount of loss on your PSTN line you must increase the ChannelRxGain setting within the Line section of the Obi configuration menu. I ultimately changed mine to 8 vs. the default 5. Without this change the "half duplex" nature of call tended to be biased to me as the talker. This had the effect of muting the audio I was receiving from the distant party during syllables which made their words difficult to understand.
Update 10/14/12: I have settled on -1 for txgain and 7 for rxgain. I also found that changing the ac impedance to the one that begins with 220 made a significant difference.

Update (12-06-13):
Although previous adjustments solved most issues I had one last troublesome audio problem. If I called someone that had relatively low audio (them to me) I found that the Obi was too sensitive in biasing the audio from me to them. This issue made them sound as if they were fading in and out whenever my handset picked up even the slightest noise (breathing). My IP phones are Aastra 57i's, they do have hot audio but so do many IP phones. The solution was to turn down the 57i tx gain setting by minus ten (-10). So lesson learned is that you need to adjust gain on the Obi and your IP phone to get the proper result. If your audio is too hot going to the Obi and your just adjusting the outgoing Obi gain you may be getting the desired volume but you are over-driving the circuits in the Obi that control audio switching and e-c-h-o.

I had been having an issue with the xmit & recv switching that the Obi does during a call. This switching is a result of the half duplex and e-c-h-o reduction nature of the device. I was experiencing changing volume that would make it difficult to hear the beginning of words and sometimes random words. The problem occured on calls originated on the Obi phone port or my Asterisk trunk.
My Obi connects to my PSTN line and then to my Asterisk box. Within the line setting configuration area of the Obi you can set ChannelTxGain & ChannelRxGain. I had changed these from the defaults (0,5) to (-1,0) which at the time worked fine for me but I discovered this change indirectly affects the balance of the switching that occurs as the conversation proceeds in each direction. I also noticed that even when I wasn't having a two way conversation if I were to dial a busy signal the volume of the signal would be changing and fading in in out.
THE FIX was to put the gains back to the defaults and the problem goes away. It would seem that if the RxGain is set too low there is not enough drive within the digital switching to bias the switch toward the receiving end on something like a busy tone. I'm sure other settings will work but the key is don't go too low on the ChannelRxGain setting.

Update: If you have a fair amount of loss on your PSTN line you must increase the ChannelRxGain setting within the Line section of the Obi configuration menu. I ultimately changed mine to 8 vs. the default 5. Without this change the "half duplex" nature of call tended to be biased to me as the talker. This had the effect of muting the audio I was receiving from the distant party during syllables which made their words difficult to understand.
Update 10/14/12: I have settled on -1 for txgain and 7 for rxgain. I also found that changing the ac impedance to the one that begins with 220 made a significant difference.

Update (12-06-13):
Although previous adjustments solved most issues I had one last troublesome audio problem. If I called someone that had relatively low audio (them to me) I found that the Obi was too sensitive in biasing the audio from me to them. This issue made them sound as if they were fading in and out whenever my handset picked up even the slightest noise (breathing). My IP phones are Aastra 57i's, they do have hot audio but so do many IP phones. The solution was to turn down the 57i tx gain setting by minus ten (-10). So lesson learned is that you need to adjust gain on the Obi and your IP phone to get the proper result. If your audio is too hot going to the Obi and your just adjusting the outgoing Obi gain you may be getting the desired volume but you are over-driving the circuits in the Obi that control audio switching and e-c-h-o.

I had been having an issue with the xmit & recv switching that the Obi does during a call. This switching is a result of the half duplex and e-c-h-o reduction nature of the device. I was experiencing changing volume that would make it difficult to hear the beginning of words and sometimes random words. The problem occured on calls originated on the Obi phone port or my Asterisk trunk.
My Obi connects to my PSTN line and then to my Asterisk box. Within the line setting configuration area of the Obi you can set ChannelTxGain & ChannelRxGain. I had changed these from the defaults (0,5) to (-1,0) which at the time worked fine for me but I discovered this change indirectly affects the balance of the switching that occurs as the conversation proceeds in each direction. I also noticed that even when I wasn't having a two way conversation if I were to dial a busy signal the volume of the signal would be changing and fading in in out.
THE FIX was to put the gains back to the defaults and the problem goes away. It would seem that if the RxGain is set too low there is not enough drive within the digital switching to bias the switch toward the receiving end on something like a busy tone. I'm sure other settings will work but the key is don't go too low on the ChannelRxGain setting.

Update: If you have a fair amount of loss on your PSTN line you must increase the ChannelRxGain setting within the Line section of the Obi configuration menu. I ultimately changed mine to 8 vs. the default 5. Without this change the "half duplex" nature of call tended to be biased to me as the talker. This had the effect of muting the audio I was receiving from the distant party during syllables which made their words difficult to understand.
Update 10/14/12: I have settled on -1 for txgain and 7 for rxgain. I also found that changing the ac impedance to the one that begins with 220 made a significant difference.

Update (12-06-13):
Although previous adjustments solved most issues I had one last troublesome audio problem. If I called someone that had relatively low audio (them to me) I found that the Obi was too sensitive in biasing the audio from me to them. This issue made them sound as if they were fading in and out whenever my handset picked up even the slightest noise (breathing). My IP phones are Aastra 57i's, they do have hot audio but so do many IP phones. The solution was to turn down the 57i tx gain setting by minus ten (-10). So lesson learned is that you need to adjust gain on the Obi and your IP phone to get the proper result. If your audio is too hot going to the Obi and your just adjusting the outgoing Obi gain you may be getting the desired volume but you are over-driving the circuits in the Obi that control audio switching and e-c-h-o.