CMX838 View Datasheet(PDF) - CML Microsystems Plc
Part Name
Description
MFG CO.
'CMX838' PDF : 71 Pages View PDF
FRS/PMR446/GMRS Family Radio Processor
CMX838
6.4.1 Audio Processing
The Audio Processing section, shown in Figure 27, supports both TX and RX operating modes with various
switch paths and enable/disable functions. The features support both end user features (e.g. digital
loudspeaker speaker volume control and digital mic gain control) and manufacturing operations (e.g. peak
deviation trim testing). Features include:
• High gain microphone input amplifier to directly support electret/condenser microphones
• Auxiliary audio input to accept signals from a second audio source e.g. an external tone generator or via
an internal path from the CMX838’s Tone Signaling Processor
• Microphone/auxiliary/discriminator source switch
• Pre-emphasis filter with enable/disable
• Digital microphone level control
• Audio filters to band limit audio signals and convert externally applied square tones to call tones
• Switch matrix to engage both ‘forward’ and ‘reverse’ external audio processing functions.
• Deviation limiter with integrated voltage reference regulates output level for constant audio RF deviation
without requiring an external voltage regulator.
• Post deviation limiter filter
• TX output to Modulator section path enable switch
• De-emphasis filter with enable/disable
• RX output digital volume control
MICOUT 3
MICIN 4
-
audio from an external
+
electret mic or a higher
level signal source Vbias
AUX I/O 2
alternate audio input e.g.
call tone signals
RXIN 1
from the
discriminator
preemph
LPF
alternate external audio processing paths
e.g. companding, scrambling, etc.
AOUT to AIN and BOUT to BIN
BOUT AOUT
27 28
AIN
BIN
25 24
HPF
LIM
voltage ref
deemph
LPF
processed TX audio to
modulation section
processed RX audio to
loudspeaker path
RXOUT 23
Figure 27: Audio Processing
2003 CML Microsystems Plc
48
D/838/8
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