Hello guys, I have a strange issue with an analog GSM gateway that when I call through the IPO, the audio only works in one direction. The phones from which the calls are being made are digital, so the calls do not go through the client's LAN network. I also tried removing the SIM cards and testing them directly in a mobile phone and I have no audio issues. I brought the client's equipment to my office and did the same test and here I did not present any audio failure, I tested with analog, digital, and IP phones and it worked perfectly. I already changed the VCM board and the complete chassis of the control unit and the result at the client's site is the same. The client also acquired a GSM IP gateway and the result was the same, that is, the audio continues to fail in one direction. Has anyone else experienced this and can give me any idea of what else I can try?