Recently I replaced my Huawei E1550 with a Huawei E173-U2 modem. Both modems are completely unlocked (and voice enabled), with latest firmware files, as per dc-files.com site. While with Huawei E1550, I was having this terrible voice-quality issue, with Huawei E173-U2, I fared much better initially (last night), and my first call went through perfectly, and I got connected to the IVR menu "5000". However, since I was facing signal-quality issues, I used AT^SYSCFG to set the modem to 2G mode, and got excellent signal. Apart from that, I don't remember making other changes, but since this morning, I am getting this 100% repeatable problem, where-in, once I call FS via my mobile, I see the usb-modem attached to FS (gsmopen EP) ringing, and get connected, but I do not hear the IVR menu anymore, but complete silence. After a while the call disconnects, and then I see console log indicating that my /dev/ttyUSB2 (control port) is probably dead, and as a result the /dev/ttyUSB1 and /dev/ttyUSB2 are removed, and /dev/ttyUSB3 and /dev/ttyUSB4 are created. If I reconfigure gsmopen.conf.xml file to use the new audio and control ports, and place another call, the same thing repeats. I've attempted this across several reboots, but is 100% repeatable. What I see in the console log: http://pastebin.com/swnz4sWf The relevant portion of the freeswitch.log file: http://pastebin.com/dNkhaGen Any ideas / clues as to what's up ? I tried going through the log file, and what I figured is that nothing seems to be received by FS on the audio port, and eventually /dev/ttyUSB2 becomes unresponsive, i.e. doesn't respond to AT-commands. Not sure though. - Jay