COMMUNICATION SEMICONDUCTORS
DATA BULLETIN
Features
• Two (12kHz/16kHz) SPM Detectors
• Standard 3.579545MHz Xtal
• Selectable Bandwidth Limits
• Excellent Speech-Band Rejection
• Low Power 3.0V to 5.0V Operation
CMX661
Pair Gain Dual SPM Detector
Advance Information
Applications
• Pair-Gain Systems
• Out-of-Band Signaling Systems
• Call Charge Applications in PBX and PABX
Line Cards
The CMX661 is a low power, Dual Subscriber Pulse Metering (SPM) Detector – two detectors on a single
chip – to indicate the presence on a telephone line of either 12kHz or 16kHz telephone call charge
frequencies. The detection frequency and bandwidth are common to both detectors and may be externally
selected. The detection sensitivity is set independently for each channel by external components and the
detector outputs can be set to a high impedance state for device multiplexing requirements in PBX and PABX
line card applications.
Flexibility of decode bandwidth settings allows the CMX661 to operate in systems where the SPM generation
is not necessarily perfectly accurate or stable. External hardwired selection of functionality economizes on the
number of host µC I/O control lines required, while the rapid response and de-response times of the CMX661
permit flexible tone length qualification by the host µC.
The CMX661 offers low (3.0V) operating voltage and power, consuming ≈750µA at 3V. It is available in low-
cost 16-pin plastic DIL and SOIC packages.
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