I have two modems plugged in my PC. One SIERRA named ttyUSB9 and another - ZTE named ttyUSB2. Usually i used only ZTE. And it is used in my ppp option script to connect via 3G-modem. But sometimes, after reboot TCL this ttyUSB's randomly change each other. So SIERRA became ttyUSB2 and ZTE became ttyUSB9. PPP option script not working till i am not change ttyUSB2 to ttyUSB9. How can i to attach ttyUSB-number to a specific modem. Or how can i recognize each ttyUSB if it impossible to attach number?