Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A Radio Interface Layer (RIL) is a layer in an operating system which provides an interface to the hardware's radio and modem on e.g. a mobile phone. The Android Open Source Project provides a Radio Interface Layer (RIL) between Android telephony services (android.telephony) and the radio hardware. It consists of a stack of two components: a RIL Daemon and a Vendor RIL. The RIL Daemon talks to the telephony services and dispatches "solicited commands" to the Vendor RIL. The Vendor RIL is specific to a particular radio implementation, and dispatches "unsolicited commands" up to the RIL Daemon. A RIL is a key component of Microsoft's Windows Mobile OS. The RIL enables wireless voice or data applications to communicate with a GSM/GPRS or CDMA2000 1X modem on a Windows Mobile device. The RIL provides the system interface between the CellCore layer within the Windows Mobile OS and the radio protocol stack used by the wireless modem hardware. The RIL, therefore, also allows OEMs to integrate a variety of modems into their equipment by providing this interface.