Brief Description
The CMX641A is a low power, system selectable 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 sensitivity, frequency and bandwidth are independently selectable for each channel, under µC control, as is the frequency of the security tone generator, which may be ASK modulated by an external signal. The CMX641A is also backwards compatible with the FX641 and MX641 dual SPM detectors, whilst offering a lower (3.0V) operating voltage and power.

FEATUREs
• Two (12kHz/16kHz) SPM Detectors
• Selectable 12kHz/16kHz ASK Generator
• Selectable Tone Follower or Packet Mode 3-State Outputs
• Excellent Speech-Band Rejection
• Hardwired Control for Non-µC Systems
• Selectable Bandwidth Limits and Stable Centre Frequency from a Standard Xtal

APPLICATIONs
• SPM for Pair-Gain Systems
• Payphone Security Applications
• Call Charge Applications in PBX and PABX Line Cards
• Out-of-Band Signalling Systems
• Low-Voltage FX/MX641 Replacement
• µC Software-Programmable Secure Payphone Call Charging Apparatus