PSTN line gain
JeremyW:
OK. I went too far I think. Set ChannelTxGain on the Line port to +3 initially but on the basis of one comment from someone who's hearing isn't the best (my error of judgement) I upped it to +5.
Today my wife took an incoming call (PSTN) and complained that her own voice echoed. Could that be down to too much Tx gain? Assuming so and unless anyone has any better suggestions I've dropped it to +2. Not sure what increments are best to use.
ianobi:
I'm afraid this is mostly a question of making changes and trying them out. I recommend setting volumes using a corded "plug-in" phone, as cordless dect phones have their own volume settings and may add confusion.
Quote
Today my wife took an incoming call (PSTN) and complained that her own voice echoed. Could that be down to too much Tx gain?
Echo may be caused by too high TX gain and/or mismatched impedance between the OBi and the land line. Although there is a theoretical impedance value to set the for the OBi (in the UK config file), in real life line conditions vary somewhat and trying a few other impedance settings can sometimes help. That's a last resort, changing TX and RX gains are the first step.
If you do not wish to bother your friends too much you can call 0800 500005 and listen to boring internal BT news to test your receive volume. Testing transmit is more difficult. If you have a spare phone you can plug into a socket on the PSTN side of your OBi, then you can listen to someone speaking on the phone attached to the OBi and get a rough idea of volume going to line - pick up the phone on the PSTN side of the OBi after the call is established. To do this dial the BT test number 17070 and select option 2 "quiet line test". This will remove all other noises such as dial tone while you test.
dBs as a measure of volume work in a logarithmic way, not a straight scale. Upping the level by 3dB will double the volume. Best to try 1dB at a time.
JeremyW:
Thanks for the wealth of info. I'll experiment...
JeremyW:
Quote from: ianobi on February 04, 2015, 02:13:59 am
I'm afraid this is mostly a question of making changes and trying them out. I recommend setting volumes using a corded "plug-in" phone, as cordless dect phones have their own volume settings and may add confusion.
Quote
Today my wife took an incoming call (PSTN) and complained that her own voice echoed. Could that be down to too much Tx gain?
Echo may be caused by too high TX gain and/or mismatched impedance between the OBi and the land line. Although there is a theoretical impedance value to set the for the OBi (in the UK config file), in real life line conditions vary somewhat and trying a few other impedance settings can sometimes help. That's a last resort, changing TX and RX gains are the first step.
If you do not wish to bother your friends too much you can call 0800 500005 and listen to boring internal BT news to test your receive volume. Testing transmit is more difficult. If you have a spare phone you can plug into a socket on the PSTN side of your OBi, then you can listen to someone speaking on the phone attached to the OBi and get a rough idea of volume going to line - pick up the phone on the PSTN side of the OBi after the call is established. To do this dial the BT test number 17070 and select option 2 "quiet line test". This will remove all other noises such as dial tone while you test.
dBs as a measure of volume work in a logarithmic way, not a straight scale. Upping the level by 3dB will double the volume. Best to try 1dB at a time.
Hmm.. I'm confusing myself. If I deliberately call out over the PSTN by using **8, volumes are OK - the other party is maybe a little quiet but I get no complaints about the volume of my voice. If they call in (always over the PSTN), the caller volume level is higher but I then get comments that I 'sound quiet'. Any more clues from that?
WelshPaul:
What exactly are the values of both the ChannelTxGain and ChannelRxGain parameters under both the phone and line port configs?
If it was me I would setup a Voipfone account on an empty SPx slot and perform an echo test by dialing 152 - When you speak into the handset anything you say is played back to you! Adjust the phone port ChannelTxGain and ChannelRxGain until you get the desirved volume levels. (Use a corded telephone)
Now remove the Voipfone account if no longer required. Next thing is to dial out over the PSTN line, any old freephone number will do and listen any recorded messag or IVR - Adjust the ChannelRxGain under line port if needed until you have a comfortable level of volume.
All that's left to do know is adjust the ChannelTxGain under line port, increase it in steps of one until people stop saying you sound quiet.
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