FSK Modem and DTMF Codec
CMX865
DTMF Decoder
Notes
Min.
Typ.
Max.
Unit
Valid input signal levels
(each tone of composite signal)
8
8
-31.0
-
2.0
dBm
Not decode level
(either tone of composite signal)
Twist = High Tone/Low Tone
Frequency Detect Bandwidth
Frequency Not Detect Bandwidth
Max level of low frequency noise (i.e. dial tone)
Interfering signal frequency <= 550Hz
Interfering signal frequency <= 450Hz
Interfering signal frequency <= 200Hz
Max. noise level wrt. signal
DTMF detect response time
DTMF de-response time
Status Register b5 high time
‘Will Detect’ DTMF signal duration
‘Will Not Detect’ DTMF signal duration
Pause length detected
-
-
-
-
-
-38.0
10.0
-
dBm
dB
%
-10.0
±2.2
-
±3.5
%
12
12
12
-
-
-
-
-
-
-
-
-
-
-
0.0
10.0
20.0
-10.0
40.0
30.0
-
-
-
-
dB
dB
dB
dB
ms
ms
ms
ms
ms
ms
ms
falses/
30mins
12, 13
-
-
14.0
40.0
-
30.0
-
-
25.0
-
-
13
Pause length ignored
Falsing performance
15.0
–
14
–
Notes:
12. Referenced to DTMF tone of lower amplitude.
13. Flat Gaussian Noise in 300-3400Hz band.
14. Mitel CM7291 test tape, 1kHz reference tone set to 775mVrms.
Receive Input Amplifier
Input impedance (at 100Hz)
Notes
Min.
10.0
Typ.
Max.
Units
Moh
m
Open loop gain (at 100Hz)
Rx Gain Control Block accuracy
10000
V/V
dB
-0.25
+0.25
© 2005 CML Microsystems Plc
39
D/865/3
CMLMICRO [ CML MICROCIRCUITS ]
