... the software by the checkpoint ID.5. Low power consumption, battery lasts for more than one year, real-time display of ... .4%Frequency tolerance range±3KHzOperating voltage2.7V—6V (3*AA Battery or 6VPower supply adapter)Sideband stray(Harmonic excluded)< -36dBmHarmonic suppression40dBMim ... that needs patrol, machine, equipment&facility check and maintenance etc walkie talkie intercom interphone reader