The CMX264 is a frequency domain scrambler for use in analog cellular phone systems. It contains separate Tx and Rx paths for full duplex operation and operates under Processor control via a simple serial interface. In the Tx path, scrambling is achieved by splitting the audio band into two parts, or sub-bands, and frequency inverting each one. The frequency at which the signal is split, the "split-point", can be either fixed or rolling between four possible settings resulting in a transmitted audio signal which is unintelligible to eavesdroppers. Descrambling is achieved by a receive device set to the same split point as the remote transmitter. Thus if the Tx and Rx devices are synchronously cycled through the same sequence of split points, a clear recovered signal will emerge at the output of the receiver. A 4.433619MHz crystal is used allowing up to four split points to be programmed. The device is designed to be compatible with existing cell-phone circuitry. The CMX264 operates at 3.0V and is available in a 24-pin SSOP (CMX264D5). 2000 MX-COM, Inc.