Calling Line Identifier

FX602

© 1998 Consumer Microcircuits Limited

8

D/602/7

The Input Signal Amplifier may also be used with an unbalanced signal source as shown in Figure 3b. The

values of R6 and R8 are as for the balanced input case.

Figure 3b : Input Signal Amplifier, unbalanced input configuration

0

100

200

300

400

500

600

700

800

900

1000

3

3.5

4

4.5

5

5.5

R8

R9

1.5.3

Bandpass Filter

Is used to attenuate out of band noise and interfering signals which might otherwise reach the FSK

Demodulator, Tone Alert Detector and Level Detector circuits. The characteristics of this filter differ in FSK and

Tone Alert modes. Most of the filtering is provided by Switched Capacitor stages clocked at 57.7kHz.

1.5.4

Level Detector

This block operates by measuring the level of the signal at the output of the Bandpass Filter, and comparing it

against a threshold which depends on whether FSK Receive or Tone Alert Detect mode has been selected.

In Tone Alert Detect mode the output of the Level Detector block provides an input to the Tone Alert Signal

Detector.