I bought this modem, hoping it had same circuitry of the one described in this page, but unfortunately it isn't! >:(
It's labeled as Telit MG10, but it's actually a Solomon SMCi250U, and it has this internal circuitry:
The IC at the bottom (behind metal cross) is labeled as MC13712F REV 3.1 CTGQ0413. No other ICs are visible in the modem, hence no 2303 USB chips are visibile.
So, how do I connect it to Arduino? :-/
Wait, I was eventually able to unpack a closed side of the module, and I found an ISP1105!
I thin it's what I need, but how do I connect Arduino to it? Which pins should I use?
alright, well it looks like what you were looking for was a serial to usb converter which you could splice out to just get to the serial lines of the module. the chip that you have identified is a usb line driver, meaning it handles the electrical, not protocol part of the transmission. it will be of no help since you need serial lines. keep looking, maybe theres a serial line buried somewhere!