AMBE-2000 Digital Voice Systems, Inc., AMBE-2000 Datasheet - Page 60

• Manufacturer Part Number: AMBE-2000
• Description: 2.0 - 9.6 KBPS Single ic For Toll-quality, Low Data Rate, Real Time Speech Compression
• Manufacturer: Digital Voice Systems, Inc.

8.5
The AMBE-2000™ is capable of detecting and generating single tones as well as dual tones. The single tones span from
156.25 Hz to 3812.5 Hz in 31.25 Hz steps.
8.6
In modern communication systems the transmitter transmits information in the form of symbols. The demodulator
takes the received signal and tries to decide which symbol was transmitted. In other words, the demodulator is
making a decision based on the received signal. For instance, in a binary system, the symbols could be represented
by a 1 and a 0. Because of interference and many other factors, these signals can be misinterpreted because of
channel degradation. Significant improvement in FEC performance can be added by setting up the receiver so that
the demodulator is making a finer estimation of the received energy prior to the decoder, this is called soft-decision
decoding. The link below describes this in more detail.
The AMBE-2000™/2020 utilizes a 4-bit soft decision decoder. The bits are defined as follows:
Visit us at
DVSI Confidential Proprietary, Subject to Change
Expanded Tone Detection and Generation
Soft Decision Decoding
www.dvsinc.com
Tone Index
(Decimal)
………….
123-127
147-254
………
http://www.mathworks.com/access/helpdesk/help/toolbox/commblks/usersguide/tutor135.shtml
122
128
143
144
145
146
255
0-4
5
6
7
Decision Value (Binary)
0000
0111
Call Progress
Call Progress
Call Progress
DTMF “D”
Tone Type
DTMF “1”
…………..
………….
No Tone
Invalid
Invalid
Invalid
Single
Single
Single
Single
Most confident 0
Least confident 0
Interpretation
………….
…………
Freq #2
1209
1633
(Hz)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
440
480
620
……………
…………
Freq #1
156.25
218.75
3812.5
187.5
(Hz)
N/A
N/A
N/A
N/A
697
941
350
440
480
Page 60