CMX264

Features:

· Ensures Privacy
· Full Duplex · Standby Mode
· High Quality Recovered Audio
· Low Height, Surface Mount Package
· 3.0V, Low Power Operation
· Fixed or Rolling Code
· Uses Split Band Inversion
· Low Current, Low Voltage
· 4.433619MHz Operation




Description

The CMX264 is a frequency domain scrambler for use in analogue cellular phone systems. It contains separate Tx and Rx paths for full duplex operation and operates under µProcessor 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 CMX264 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. CMX264 is designed to be compatible with existing cellphone circuitry.