Calling Line Identifier
FX602
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
1000
900
R8 and R9 : k ohms
800
700
600
500
400
300
200
100
0
3
3.5
4
Nominal V
DD
Figure 3c : Input Signal Amplifier, optimum values of R8 and R9 vs V
DD
R8
R9
4.5
5
5.5
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.
©
1998 Consumer Microcircuits Limited
8
D/602/7
CMLMICRO [ CML MICROCIRCUITS ]
