Brief Description
The CMX631A is a low-power, system-selectable Subscriber Pulse Metering (SPM) detector that indicates the presence of either 12kHz or 16kHz telephone call-charge frequencies on a telephone line.
Deriving its input directly from the telephone line, input amplitude/sensitivities are component adjustable to the user's national ‘Must/Must-Not Decode’ specifications via an on-chip input amplifier. The 12kHz and 16kHz frequency limits are accurately defined by the use of an external 3.579545MHz telephone-system Xtal or clock-pulse input.
The CMX631A demonstrates exceptional 12kHz and 16kHz performance in the presence of both voice and noise. This device may operate from a single or differential analogue signal input, from which two individual logic outputs will be produced; a Tone Follower Output and a Packet Mode Output.

FEATUREs and Applications
• Detects 12kHz or 16kHz SPM Frequencies
• Tone Follower and Packet Mode Outputs
• High Speech-Band Rejection Properties
• Low Power Operation (2.7V <0.8mA)
• Call Charge Applications on PABX Line Cards
• Complex and/or Simple Telephone Systems
• Remote Telephone/Payphones