CMX138 CML Microcircuits, CMX138 Datasheet - Page 69

• Manufacturer Part Number: CMX138
• Description: Audio Scrambler and Sub-Audio Signalling Processor
• Manufacturer: CML Microcircuits

Audio Scrambler and Sub-Audio Signalling Processor
© 2008 CML Microsystems Plc
Notes:
AC Parameters (cont.)
Analogue Channel Audio Filtering
Audio Scrambler
Audio Expandor
Pass-band (nominal bandwidth):
Pass-band Gain (at 1.0kHz)
Pass-band Ripple (wrt gain at 1.0kHz)
Stop-band Attenuation
Residual Hum and Noise
Pre-emphasis
De-emphasis
Inversion frequency
Pass-band (assuming 3300Hz inversion
frequency)
Input Signal Range
Received audio
12.5kHz channel transmitted audio
25kHz channel transmitted audio
91
92
93
94
95
96
97
98
99
The receiver audio filter complies with the characteristic shown in Figure 6. The
high pass filtering removes sub-audio components from the audio signal.
The 12.5kHz channel filter complies with the characteristic shown in Figure 9.
The 25kHz channel filter complies with the characteristic shown in Figure 8.
The pre-emphasis filter complies with the characteristic shown in Figure 10
The de-emphasis filter complies with the characteristic shown in Figure 7.
Measured in a 30kHz bandwidth.
AV
Use of a scrambler inversion frequency other than 3300Hz will shift the scrambled
voice signal outside the audio band, so that some of the signal will be lost in the
channel filter. The result is that the descrambled voice signal will have a restricted
bandwidth. The limits quoted are subjective and relate to the onset of a loss of
speech intelligibility.
-6dB points.
DD
= 3.3V.
Page 69
Notes
91
92
93
96
94
95
98
99
97
2632
Min.
−2.0
33.0
300
300
300
300
–
–
–
–
–
3300
Typ.
−50
+6
−6
0
–
–
–
0
–
–
–
Max.
3300
2550
3000
3496
3000
+0.5
0.55
–
–
–
–
–
D/138_FI1.0/5
dB/oct
dB/oct
Vrms
CMX138
Unit
Hz
Hz
Hz
dB
dB
dB
dB
Hz
Hz