Overview

This is a small break-out board for miniPCIe (mPCIe) type cellular / WWAN modems.

It allows you to insert a mPCIe modem from any vendor, and it will provide you with:

mini USB socket for connection to a USB Host (like your PC/Laptop or Embedded System)
5V DC input for power supply (USB supply usually insufficient for a modem)
all unused mPCIe pins on a 2.54mm break-out header
SIM card slot for a 2FF-sized SIM, USIM or RUIM card

Particularly the break-out header is useful to get access to various signals exported in a non-standard fashion by some modem models, such as digital audio PCM.