MAX4146x ISM/SRD Transmitters Analog Devices MAX4146x UHF Sub-GHz ISM/SRD Transmitters designed to transmit Frequency-Shift Keying (FSK), Amplitude-Shift Keying (ASK), or Gaussian (G)FSK data with an I2C interface in the 286MHz to 960MHz frequency range. The devices integrate a fractional phase-locked-loop (PLL) so that a single crystal can be used to generate commonly used worldwide sub-GHz frequencies. The fast response time of the PLL allows for frequency-hopping spread spectrum protocols for increased range and security. The Analog Devices MAX4146x transmitters can be used for Industrial, Scientific, and Medical (ISM) or Short Range Devices (SRD) applications.