Hi Otto, Thanks for the advice. In your second paragraph the opposite was actually the case. The E1 voice-ports were originally showing a-law, and had distortion. I hard set u-law on the E1 ports between the gateway and PSTN router and the distortion went away. Perhaps that is what you meant?
I took a look at the link you included. I'll have to do some testing but my main question is how is this handled in the real world at the provider level? Thanks, Jason From: Otto Sanchez [mailto:o...@ipexpert.com] Sent: Friday, March 12, 2010 4:59 AM To: Jason Granat Cc: <ccie_voice@onlinestudylist.com> Subject: Re: [OSL | CCIE_Voice] PSTN Call Distortion Between T1/E1 Hello Jason, E1's and T1's will always use a-law and u-law companding mechanism respectively, this is used to give more "resolution" to low voice frequencies when digitizing an analog signal (the mechanism is also used in the other end for digital to analogue conversion), each mechanism is designed exclusively to work with its voice digital standard and cannot be used conversely, In that sense, my guess is that before applying that command in your E1 port, the companding type was u-law, you can verify this using the sh voice port command (perhaps the default configuration of a-law was somehow overwritten by a cptone command in the same port configuration), and when you hardcoded the a-law companding type everything worked as expected, I also found a note in the Cisco IOS Voice Port Configuration Guide, which says that the command is used when cross-connecting in a local router, http://www.cisco.com/en/US/partner/docs/ios/voice/voiceport/configuration/guide/vp_cfg_digital_vps_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1009871 HTH, On Thu, Mar 11, 2010 at 2:37 PM, Jason Granat <j...@slash128.com<mailto:j...@slash128.com>> wrote: So I've got this partially figured out. It had to do with the compand-type. E1 was a-law and T1 was u-law. I set the E1 side for u-law and it sounds correct now. The final thing I am trying to figure out is how to 'trans-compand' (if that is the correct term) on the PSTN gateway. As it sits I had to change the compand-type between the PSTN and E1 gateway. I don't have experience with foreign connectivity so maybe this is the way it is done in the real world but I am thinking that perhaps the E1 site may not want or be able to change their compand-type, so can it be changed at the PSTN level between a-law and u-law locations? Thanks, Jason From: Jason Granat Sent: Thursday, March 11, 2010 9:46 AM To: <ccie_voice@onlinestudylist.com<mailto:ccie_voice@onlinestudylist.com>> Subject: PSTN Call Distortion Between T1/E1 Perhaps this is something simple that I am overlooking but I have the generic setup running in my home lab with 3 gateways and one PSTN router. 2 of the gateways are T1 and one is E1. The PSTN router is also running CME with a 7960 to simulate PSTN destinations. Calls from any site to the PSTN phone are fine. Calls between T1 sites are fine. Calls between T1 and E1 sites are distorted, like the gain is way too high. I tried playing with the gain on the voice-port but no luck. I'm not finding much online or in Cisco docs. Any suggestions? Thanks, Jason ________________________________ http://slash128.com _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com<http://www.ipexpert.com> -- Regards, Otto Sanchez CCIE #25592 (Voice) Support Engineer - IPexpert, Inc. URL: http://www.IPexpert.com ________________________________ http://slash128.com
_______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
