Hi, In interfacing FWT to Asterisk, need to know the type of Manufacturer, AT Command, line control, DSP or audio analog/PCM. For stability better using the same type. Need to change too, the source program inside asterisk channel module to comply with the devices. As 1 year ago for my client, I used Samsung S3C2440 Processor behind 1 asterisk server to handle Outbound/Inbound 30 X E1 = 300 GSM/CDMA Siemen/Huawei. Working nice.