It is a digital speech encryption module for conventional analog communication systems like Cordless Phones, VHF/HF radio sets etc. It is infact a complete digital baseband radio. The underlying communication waveform offers a bandwidth of 3 KHz and supports half duplex operation
REM takes analog speech signal at its input, digitize it and then compress it using speech codec to produce a bit stream. This bit stream is encrypted using standard cipher algorithms like DES, AES or custom developed cipher algorithms. The encrypted speech is fed to baseband software defined radio in REM where it goes through a series of digital communication blocks in order to make it compatible with the communication channel. REM outputs the encrypted speech band analog signal. This signal is transmitted over the channel using a software defined or hardware modem.
Digital encryption offers a higher level of security and is widely used nowadays. The price for this strategic level of security is usually the need of a digital transmission with a larger bandwidth, high speed processing platform and complex system design involving the use of complete modem and hardware modifications.
