Thank you for your reply,
yes, i mean pins, one for Rx and one for Tx
may be it is not necessary soldering, because it's possible to use jumpers, breadboard, usb cable and not more others for experimental assembly
for connect Sim900 as this "http://www.futurashop.it/allegato/7100-FT971.asp?L2=MODULI%20GSM&L1=MODULI%20GSM%20E%20SISTEMI%20GPS&L3=&cd=7100-FT971&nVt=&d=65,00
" with arduino i think 2 ways:
1 - female - female jumpers
2 - male - female jumpers, mounting components on breadboard
Your right, i need to remember power and ground
What do you think ? For library i need only of sim900.h, SoftwareSerial.h and inetGsm.h ?
For appropriate power i think to cellular slim battery 1000mAh when usb cable is disconnected .