The RFM22B-868-S2 is a radio module made by Hope Microelectronics. It is part of the RFM22B series, which is an ultra-low power single-chip FSK/GFSK/OOK transceiver for the 868MHz ISM band. It operates at a maximum data rate of 300kbps and has a power output of up to 100mW (20dBm). The module incorporates the functions of a digital baseband modem, RF transceiver, synthesizer and crystal oscillator, and has integrated antenna switching. It supports “listen before talk” for channel sharing and FCC compliant digital transmission techniques. The module also has a low current usage in receive and sleep modes and a high level of immunity to interference. The module measures just 14.7 x 14.7 mm, giving it a significantly reduced form factor when compared to existing radio solutions.