CMX264
Frequency Domain
Split Band Scrambler
D/CMX264/1
August 1999
Advance Information
1.0
Features
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Ensures Privacy
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Full Duplex
High Quality Recovered Audio
Low Height, Surface Mount Package
3.0V, Low Power Operation
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Fixed or Rolling Code
Standby Mode
Uses Split Band Inversion
Low Current, Low Voltage
4.433619MHz Operation
1.1
Brief 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 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 cellphone circuitry.
©
1999
Consumer Microcircuits Limited
CMLMICRO [ CML MICROCIRCUITS ]
