FX641

` Two (12kHz/16kHz) SPM Detectors on a Single Chip
` Detects 12kHz and 16kHz SPM Frequencies
` Xtal Accuracy; Stable Frequency Limits
` "Controlled" (C) and "Fixed" Signal Sensitivity Modes
` Selectable Tone Follower or Packet Mode Outputs
` High Speech-Band Rejection Properties
` "Output Enable" Multiplexing Facility
` Call-Charge Applications on PABX Line Cards

To enable the FX641 to operate correctly to most national 12kHz and 16kHz SPM specifications, the input sensitivity can be accurately adjusted and set.

There are two different pin-selectable modes of sensitivity setting available to the FX641: Controlled Sensitivity Mode and Fixed Sensitivity Mode

The Controlled Sensitivity mode allows the sensitivity setting from a Controller via a 6-bit serial data input. This same serial input also sets operation (bit 0) to either 12kHz or 16kHz systems. Both channels are set identically.

The Fixed Sensitivity mode allows the sensitivity of each channel to be set to a fixed "gain" by external components at the input amplifiers. Operation to either 12kHz or 16kHz is by the System Select input.

The FX641 is a low-power, system-selectable Dual Subscriber Private 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.

Under Processor control via a common serial interface, each channel of the FX641 will detect call-charge pulses from a telephone line and provide a digital output for recording, billing or security purposes.

A common set of external components and a stable 3.579545MHz Xtal/clock input ensures that the FX641 adheres accurately to most national "Must and Must-Not" decode band-edges and threshold levels.

The digital output is pin-selectable to one of three modes:
(1) Tone Follower mode -a logic level for the period of a correct decode.
(2) Packet mode -respond/de-respond after a cumulative period of tone or notone in a preset period.
(3) High-impedance output -for device multiplexing.

For non-Processor systems a preset sensitivity/system input allows external channel level and system setting.

FX641, which is suitable for PBX and PABX line-card and remote telephone installations, is available in compact 24-pin plastic DIL and small outlin (S.O.I.C.) packages.

The FX641 requires approximately 4.5mA at 5-volts.