CMX882 데이터 시트보기 (PDF) - CML Microsystems Plc

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CMX882

FRS Signalling Processor

CML Microsystems Plc 

FRS Signalling Processor

CMX882

1.5.3.1 Receiving Voice Band Signals

When a voice based signal is being received, it is up to the µC, in response to signal status information

provided by the CMX882, to control muting/enabling of the voice band signal to the AUDIO output.

The discriminator path through the device has a programmable gain stage. Whilst in receive mode this

should normally be set to 0dB (the default) gain.

Receive Filtering

The incoming signal is filtered, as shown in Figure 5, to remove sub-audio components and to minimise

high frequency noise. When appropriate the voice signal can then be routed to the AUDIO output.

10

250Hz

0

-10

Filter response

-20

-30

Template

-40

300Hz

3kHz

-50

-60

10Hz

100Hz

1000Hz

Frequency (Hz)

10000Hz

100000Hz

Figure 5 Rx Audio Filter Frequency Response

De-emphasis

Optional de-emphasis at -6dB per octave from 300Hz to 3000Hz (shown in Figure 6) can be selected to

facilitate compliance with TIA/EIA-603.

16

12

8

4

0

dB

-4

-8

-12

0dB/octave

+1dB

0dB

-3dB

-6dB/octave

-16

-20

100

-18dB/octave

1000

Frequency (Hz)

10000

Figure 6 De-emphasis Curve for TIA/EIA-603 Compliance

 2004 CML Microsystems Plc

18

D/882/7

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