Digital Voice Systems VC-20-ATC-10B User manual

The Speech Compression Specialists
DIGITAL VOICE SYSTEMS,INC.
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VC-20ATC-10b Vocoder Board User’s Manual
The Speech Compression Specialists
DIGITAL VOICE SYSTEMS,INC.
VC-20™ ATC-10B Vocoder Board
USERS MANUAL
Version 1.0
August, 1999

VC-20ATC-10B Vocoder Board User’s Manual
VC-20ATC-10b Vocoder Board User’s Manual
The Speech Compression Specialists
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VC-20™ ATC-10B Vocoder Board
User’s Manual
Copyright , 1999
Digital Voice Systems, Inc
234 Littleton Road
Westford, MA 01886
This document may not, in whole or in part be copied, photocopied, reproduced, translated, or reduced to any electronic
medium or machine readable form without prior consent in writing from Digital Voice Systems, Incorporated.
Every effort has been made to ensure the accuracy of this manual. However, Digital Voice Systems, Inc. makes no
warranties with respect to the documentation and disclaims any implied warranties of merchantability and fitness for a
particular purpose. Digital Voice Systems, Inc. shall not be liable for any errors or for incidental or consequential damages in
connection with the furnishing, performance, or use of this manual or the examples herein. The information in this document
is subject to change without notice.
Trademarks
VC-20ATC-10b Vocoder Board is registered trademarks of Digital Voice Systems, Inc. Other product names mentioned
may be trademarks or registered trademarks of their respective companies and are the sole property of their respective
manufacturers.
All Rights Reserved
Data subject to change

License and Warranty
VC-20ATC-10b Vocoder Board User’s Manual
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VC-20™ATC-10b Vocoder Board END USER License Agreement
1.0 Preliminary Statements and Definitions
1.1 "Voice Codec" shall mean the hardware, software and
associated documentation referred to in the invoice or shipping
papers accompanying this agreement for which END USER has
requested a license, and any derivative works thereof, including
modifications, enhancements and extensions made by or for
Digital Voice Systems, Inc. (DVSI) and including circuit diagrams,
timing diagrams, programmable logic software, logic diagrams,
layouts, operating instructions and user manuals.
1.2 "AMBE™ Software" shall mean the speech coding
software and/or firmware provided as part of the Voice Codec.
This software is contained in the Read Only Memories (ROMS,
EPROMS, EEPROMS, etc...) which are included as part of the
Voice Codec. This software includes any derivative works which
have as their source the software contained in the Read Only
Memories, and it includes the software contained in any future
Read Only Memories which DVSI may provide END USER for use
in the Voice Codec.
1.3 "Designated Site" shall mean the location of the Voice
Codec.
1.4 "Proprietary Information" shall mean the information
which DVSI desires to protect against unrestricted disclosure or
competitive use and which is designated as such in writing by DVSI
or is disclosed orally and within thirty (30) days thereafter is
reduced to tangible form pursuant to this License.
1.5 DVSI represents that it owns certain “Proprietary Rights”
in the Technology and the AMBEVoice Compression Software,
including patent rights in the Technology, and patent rights,
copyrights, and trade secrets in the AMBEVoice Compression
Software.
2.0 License Granted
2.1 Subject to the conditions herein and upon initial use of the
AMBE™ Software within the VC-20™ ATC-10b Vocoder Board,
DVSI hereby grants to END USER a non-exclusive, limited license
to use the AMBE®Voice Compression Software in machine
readable form solely on the VC-20™ ATC-10b Vocoder Board.
Title to the AMBE®Voice Compression Software remains with
DVSI. No license is granted for use of the AMBE®Voice
Compression Software on other than the VC-20™ ATC-10b
Vocoder Board. No license, right or interest in any trademark,
trade name or service mark of DVSI is granted under this
Agreement.
2.2 END USER shall not copy, extract, de-compile, reverse
engineer or disassemble the AMBE®Voice Compression Software
contained in the VC-20™ ATC-10b Vocoder Board.
2.3 Transfer of License
(a) END USER may transfer the AMBE™ Software and all
rights under this agreement to a third party together with a copy
of this Agreement provided that END USER provides DVSI with a
written notification of the transfer and provided that the third
party agrees in writing to accept all the terms and conditions of
this agreement. Upon any such transfer, END USER's rights
under this Agreement shall terminate pursuant to Section 3.0.
(b) END USER may relocate the Voice Codec, and the
subsequent location shall then be considered the Designated Site.
(c) Except as provided in this Section 2.2, this Agreement,
the AMBE™ Software and any other information provided by
DVSI to END USER and any licenses and rights granted hereunder,
may not be sold, leased, assigned, sublicensed or otherwise
transferred, in whole or in part, by END USER.
2.4 END USER shall not de-compile, reverse engineer or
disassemble the AMBE™ Software.
3.0 Term and Termination
3.1 This Agreement is effective upon initial use of the
AMBE™ Software on the Voice Codec and shall remain in effect
until terminated in accordance with this agreement.
3.2 This Agreement shall terminate automatically without
notice from DVSI if END USER fails to comply with any of the
material terms and conditions herein. END USER may terminate
this Agreement at any time upon written notice to DVSI
certifying that END USER has complied with the provisions of
Section 3.3.
3.3 Upon termination of this Agreement for any reason, END
USER shall: (i) have no further rights to the AMBE™ Software;
(ii) discontinue all use of the AMBE™ Software; and (iii) destroy
or, at DVSI's option, return all copies of the AMBE™ Software.
4.0 Payments
4.1 In consideration of the hardware, software, and associated
materials provided as part of the VC-20™ ATC-10b Vocoder
Board, and in consideration of the license and rights in the
AMBE™ Software granted by DVSI, and in consideration of
DVSI's performance of its obligations hereunder, END USER
agrees to pay to DVSI the fee specified in DVSI's invoice.
4.2 In consideration of the materials provided as part of VC-
20™ ATC-10b Vocoder Board, and in consideration of the license
and rights in the AMBEVoice Compression Software granted by
DVSI, and in consideration of DVSI's performance of its
obligations hereunder, END USER agrees to pay to DVSI the fee
specified in DVSI's invoice.

License and Warranty
VC-20ATC-10b Vocoder Board User’s Manual
5.0 Proprietary Notices
5.1 END USER shall not remove any copyright or proprietary
notice on the on the AMBEVoice Compression Software or VC-
20™ ATC-10b Vocoder Board.
6.0 Proprietary Information
6.1 The parties agree that the AMBEVoice Compression
Software shall be considered Proprietary Information.
6.2 Except as otherwise provided in this Agreement, END
USER shall not use, disclose, make, or have made any copies of
the Proprietary Information, in whole or in part, without the
prior written consent of DVSI.
6.3 END USER shall make reasonable efforts to notify and
inform its employees having access to the Proprietary
Information of END USER's limitations, duties and obligations
regarding nondisclosure and copying of the AMBE™ Software.
Proprietary Information shall be used only by employees of
END USER and only at the Designated Site, except as provided
under this agreement.
6.4 END USER shall have no obligations for disclosure or use
of Proprietary Information which: (i) is already known to END
USER, at time of disclosure by DVSI; (ii) is or becomes publicly
known through publication, inspection of product or otherwise
through no wrongful act of END USER; (iii) is received from a
third party without restriction and without breach of this
Agreement; (iv) is independently developed by END USER; (v) is
disclosed to a third party by or on behalf of DVSI without
restriction; or (vi) is approved for release or use by written
authorization of DVSI.
6.5 Notwithstanding any termination pursuant to Section 3.0,
the obligations set forth in this Section 6.0 shall survive
termination of this Agreement.
7.0 Limited Warranty
7.1 DVSI warrants the VC-20™ ATC-10b Vocoder Boardand
the AMBE™ Software to be free from defects in materials and
workmanship under normal use for a period of ninety (90) days
from the date of delivery. DVSI further warrants that the VC-
20™ ATC-10b Vocoder Board and the AMBE™ Software
operate in accordance with the written specifications delivered to
END USER with the Voice Codec.
7.2 Except as stated in Section 7.1, the VC-20™ ATC-10b
Vocoder Board and AMBE™ Software are provided "as is"
without warranty of any kind. DVSI does not warrant, guarantee
or make any representations regarding the use, or the results of
the use, of the Voice Codec or AMBE™ Software with respect to
its correctness, accuracy, reliability, currentness or otherwise.
The entire risk as to the results and performance of the VC-20™
ATC-10b Vocoder Board or AMBE™ Software is assumed by the
END USER. After expiration of the warranty period, END
USER, and not DVSI or its employees, assumes the entire cost of
any servicing, repair or correction of the Voice Codec or the
AMBE™ Software.
7.3 DVSI warrants that it has the right to enter into this
Agreement and to grant a license to use the AMBE™ Software to
END USER.
7.4 Except as specifically set forth in this Section 7.0, DVSI
makes no express or implied warranties including, without
limitation, the warranties of merchantability or fitness for a
particular purpose or arising from a course of dealing, usage or
trade practice, with respect to the Voice Codec or AMBE™
Software. Some states do not allow the exclusion of implied
warranties, so the above exclusion may not apply to END USER.
No oral or written information or advice given by DVSI or its
employees shall create a warranty or in any way increase the
scope of this warranty, and END USER may not rely on any such
information or advice. The limited warranties under this section
7.0 give END USER specific legal rights, and END USER may
have other rights which vary from state to state.
8.0 Limitation of Liability
8.1 In no event shall DVSI be liable for any special, incidental,
indirect or consequential damages resulting from the use or
performance of the Voice Codec or VC-20™ ATC-10b Vocoder
Board whether based on an action in contract, tort (including
negligence) or otherwise (including, without limitation, damages
for loss of business profits, business interruption, and loss of
business information), even if DVSI or any DVSI representative
has been advised of the possibility of such damages.
8.2 Because some states do not allow the exclusion or
limitation of liability for consequential or incidental damages, the
above limitations may not apply to END USER.
8.3 DVSI's maximum liability for damages arising under this
Agreement shall be limited to 20% (twenty percent) of the fees
paid by END USER for the particular Voice Codec or VC-20™
ATC-10b Vocoder Board which caused the damages or that is the
subject matter of, or is directly related to, the cause of action.
9.0 Taxes
9.1 All payments required under Section 4.0 or otherwise
under this Agreement are exclusive of taxes and END USERagrees
to bear and be responsible for the payment of all such taxes
(except for taxes based upon DVSI's income) including, but not
limited to, all sales, use, rental receipt, personal property or other
taxes which may be levied or assessed in connection with this
Agreement.
10.0 Export
10.1 United States export laws and regulations prohibit the
exportation of certain products or technical data received from

AMBE-1000™ Vocoder Chip User’s Manual
AMBE-1000™ Vocoder Chip User’s Manual
The Speech Compression Specialists
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DVSI under this Agreement to certain countries except under a
special validated license. As of May 20, 1996 the restricted
countries are: Libya, Cuba, North Korea, Iraq, Serbia, Montenegro,
and Iran. The END USER hereby gives its assurance to DVSI that
it will not knowingly, unless prior authorization is obtained from
the appropriate U.S. export authority, export or re-export,
directly or indirectly to any of the restricted countries any
products or technical data received from DVSI under this
Agreement in violation of said United States Export Laws and
Regulations. DVSI neither represents that a license is not required
nor that, if required, it will be issued by the U.S. Department of
Commerce. Licensee shall assume complete and sole
responsibility for obtaining any licenses required for export
purposes.
11.0 Governing Law
11.1 This Agreement is made under and shall be governed by
and construed in accordance with the laws of the Commonwealth
of Massachusetts, except that body of law governing conflicts of
law. If any provision of this Agreement shall be held
unenforceable by a court of competent jurisdiction, that provision
shall be enforced to the maximum extent permissible, and the
remaining provisions of this Agreement shall remain in full force
and effect.
12.0 Notices
12.1 Any notices to DVSI which may be given hereunder shall
be in writing and sent to: Digital Voice Systems Inc., 234
Littleton Road, Westford, MA., 01886, U.S.A.

Contents
VC-20ATC-10b Vocoder Board User’s Manual i
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TABLE OF CONTENTS
Section 11VC-20™ -ATC-10B INTRODUCTION............................................... 1
1.1 GENERAL INFORMATION...................................................................................1
Section 22VC-20 AMBE™ VOCODER BOARD OVERVIEW................................. 3
2.1 ADVANCED MULTI-BAND EXCITATION (AMBEVOCODER)...........................3
2.2 VC-20-ATC-10B VOCODER BOARD BASIC OPERATION..........................3
2.3 SPECIAL HANDLING AND STORAGE PRECAUTIONS ........................................4
Section 33BOARD SET-UP &CONFIGURATION................................................... 5
3.1 CONNECTION SPECIFICATIONS........................................................................5
3.2 DIN41612 96-PIN CONNECTOR SPECIFICATIONS..........................................6
3.3 VC-20-ATC-10BCONNECTOR SIGNALS........................................................7
3.4 VC-20-ATC-10B CONNECTOR SIGNALS .......................................................8
3.5 SILENCE FRAME DESIGNATION.....................................................................10
3.6 VC-20-ATC-10B ON-BOARD JUMPERS CONNECTOR SIGNALS .................11
3.7 VC-20-ATC-10B DTMF TONE DATA ..........................................................12
Section 44DVSISERVICES AND SUPPORT SOLUTIONS....................................13
4.1 TECHNICAL SUPPORT....................................................................................13
4.2 CUSTOMER SERVICE................................ERROR!BOOKMARK NOT DEFINED.
4.3 ADDITIONAL MANUALS ...................................................................................13

Section 1-VC-20™ -ATC-10b Introduction
VC-20ATC-10b Vocoder Board User’s Manual page 1
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1VC-20™ -ATC-10b Introduction
1.1 General Information
The Digital Voice Systems, Inc. (DVSI) VC-20™ -ATC-10b voice codec is a full-
duplex real-time voice processing board. The VC-20™ -ATC-10b contains
proprietary software which implements the Advanced Multi-Band Excitation™
(AMBE™) voice coding algorithm. DVSI grants a licence to its customers to use this
software according to the terms established in the attached AMBE™ Software END
USER License Agreement. Use of the VC-20™ -ATC-10b, or any portion thereof,
signifies acceptance of these licensing terms.
The VC-20™ -ATC-10b operates by digitizing an analog speech signal using an on-
board A-to-D converter. This digitized speech is then processed by the encoder and
converted into a data bit stream. This bit stream is output to a modem or similar device.
Simultaneously, the VC-20™ -ATC-10b receives a data bit stream from a modem or
similar device. This received bit stream is processed by the decoder and converted into a
synthetic speech signal which is then converted into an analog signal using the on-board
D-to-A converter. The encoder and decoder are fully asynchronous.
The 4.8 kbps data stream consists of 3.6 kbps of Speech data and 1.2 kbps of Error
Correction Code data. This version of the VC-20™ -ATC-10b software produces high
quality speech at bit error rates up to 4%.

Section 2–VC-20 AMBE™ Vocoder Board Overview
VC-20ATC-10b Vocoder Board User’s Manual page 3
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2VC-20 AMBE™ Vocoder Board Overview
2.1 Advanced Multi-Band Excitation (AMBEVocoder)
The Advanced Multi-Band Excitation (AMBEVocoder) technology is based on the
Multi-Band Excitation (MBE) speech model. This speech model provides a unique
speech coding framework which results in a number of advantages over linear prediction
based speech coders such as CELP, RELP, VSELP, MELP, ECELP, MP-MLQ, and
LPC-10, etc. .(1)
The AMBEvoice coder (vocoder) was first developed in the mid 1990’s by Digital
Voice Systems, Incorporated. The vocoder maintains speech intelligibility and
naturalness at rates as low as 2.4 kbits/sec. The AMBEVocoder system is less
complex than either CELP or VSELP, and therefore, it is easily integrated into low-cost,
low-power, communication integrated circuits.
2.2 VC-20-ATC-10b Vocoder Board Basic Operation
Connections are made to the VC-20™ -ATC-10b using the attached DIN 41612
connector which is described in Sections 4 and 5. The user must supply the VC-20-MTR
with a 5v digital power supply and a +/-5v analog power supply. It is preferable to
decouple the analog supply from the digital supply by using separate power supplies.
The VC-20™ -ATC-10b can be connected to a modem or similar device as shown in
Figure 3. The modem or the VC-20™ -ATC-10b can generate the clock and framing
signals TXCK, FMEN, RXCK and FMDE. The modem reads the data from the encoder
on the data lines TXD3-0. Simultaneously the decoder reads data from the modem on
data lines RXD3-0. The frame signals FMEN and FMDE are used to signify the beginning
of each data frame for the encoder and decoder, respectively. The required timing
relationship between these signals is shown in Figure 5. In order to operate in this mode,
jumpers 5-14 should be disconnected. If the VC-™ -ATC-10b is generating the clocks
and frames, then jumpers 1-4 should be connected, otherwise, they should be
disconnected.

Section 2-VC-20 AMBE™ Vocoder Board Overview
VC-20ATC-10b Vocoder Board User’s Manual
page 4
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The VAD signal should be held low to enable the onboard Voice/Silence detection and
Adaptive Comfort Noise features. When enabled the ENSLNCE signal is switched to
indicate the presence of Voice. If the VAD signal is held high or left disconnected, both
Voice/Silence detection and Adaptive Comfort Noise are disabled, and the ENSLNCE
signal always indicates voice.
Note that for proper operation any background noise present in the speech must be short
term stationary and have a level less than -25 dBm0.
2.3 Special Handling and Storage Precautions
CAUTION
Handling Instructions
Although the VC-20 AMBE™ Vocoder Board incorporates input protection circuitry,
to avoid damage from the accumulation of a static charge, industry standard
electrostatic discharge precautions and procedures must be employed during handling
and installing.
Storage
To insure maximum shelf life in long term storage, VC-20 AMBE™ Vocoder Board
should be kept in a moisture controlled package at <40°C and <90% RH.

Section 6 –VC-20™ ATC-10b Vocoder Board Advanced Features
VC-20ATC-10b Vocoder Board User’s Manual page 5
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3Board Set-up & Configuration
3.1 Connection Specifications
Connector type
Physical: 100 mm (Single Euro-card [3U]) height (see Figure 6)
DIN 41612 Connector (male)
Analog Input: Type single-ended
Impedance 600 ohm
Sensitivity 0 dBm0 = 0 dBm
Sinusoidal Overload +3.17 dBm0
Nominal Level -23 dBm0 (average speech level)
Dynamic Range +/-10 dB (relative to Nominal Level)
Noise Level -72 dBm0
Bandwidth 0 -3700 Hz.
Analog Output: Type single-ended
Impedance low impedance output, capable of driving a 600 ohm load
Sensitivity 0 dBm0 = 0 dBm
Sinusoidal Overload +3.17 dBm0
Nominal Level -23 dBm0 (average speech level)
Dynamic Range +/-10 dB (relative to Nominal Level)
Noise Level -72 dBm0
Bandwidth 20 -3700 Hz.
Digital Interface: TTL compatible
Power: 2 watts @ 5v digital, .2 watts @ +/-5v analog

Section 6 –VC-20™ATC-10b Vocoder Board Advanced Features
VC-20ATC-10b Vocoder Board User’s Manual
page 6
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3.2 DIN41612 96-pin ConnectorSpecifications
ROW C ROW B ROW APin
No. Function Name Function Function Name
1 Dig. Pwr. VCC Rsvd. Dig. Pwr. VCC
2 Dig. Pwr. VCC Rsvd. Dig. Pwr. VCC
3 Gnd. GND Rsvd. Gnd. GND
4 Output TXD3 Rsvd. Output TXD0
5 Rsvd. Rsvd. Input TXCK
6 Input FMEN Rsvd. Output RUN
7 Rsvd. Rsvd. Output RESX
8 Gnd. GND Rsvd. Gnd. GND
9 Input RXD3 Rsvd. Input RXD0
10 Rsvd. Rsvd. Input RXCK
11 Input FMDE Rsvd. Rsvd.
12 Rsvd. Rsvd. Rsvd.
13 Gnd. GND Rsvd. Gnd. GND
14 Rsvd. Rsvd. Rsvd.
15 Output TXD2 Rsvd. Input DINRS
16 Output TXD1 Rsvd. Rsvd.
17 Rsvd Rsvd. Output DTMF_DET
18 Input RXD2 Rsvd. Rsvd.
19 Input RXD1 Rsvd. Rsvd.
20 Gnd. GND Rsvd. Gnd. GND
21 Rsvd Rsvd. Output. DTMF_DAT
22 Rsvd. Rsvd. Input VAD
23 Rsvd. Rsvd. Input ECHO
24 Input GO Rsvd. Rsvd.
25 Rsvd. Rsvd. Rsvd.
26 Gnd. GND Rsvd. Gnd. GND
27 Anlg Pwr. +5v analog Rsvd. Anlg Pwr. +5v analog
28 Anlg Pwr. -5v analog Rsvd. Anlg Pwr. -5v analog
29 Output VFRO Rsvd. Input VFXI
30 Anlg Gnd AGND Rsvd. Anlg Gnd AGND
31 Gnd. GND Rsvd. Gnd. GND
32 Gnd. GND Rsvd. Gnd. GND
Note: Pwr. = POWER
Input = INPUT to the VC-20-MR2
OUTPUT = OUTPUT from the VC-20-MR2

Section 6 –VC-20™ ATC-10b Vocoder Board Advanced Features
VC-20ATC-10b Vocoder Board User’s Manual page 7
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Rsvd. = RESERVED (Leave Unconnected)
Note: Many Reserved signals are used to monitor the internal state of the VC-20™ -ATC-10b. To
ensure proper operation all reserved signals must be left unconnected.
3.3 VC-20-ATC-10BConnector Signals
Name Dir Description
VCC Pwr. Digital +5v +/-5%
GND Pwr. Digital Ground
+5v Pwr. Analog +5v +/-10%
-5v Pwr. Analog -5v +/-10%
GND Anlg Pwr. Analog Ground
TXD3 OTransmit data channel
TXD2 OTransmit data channel
TXD1 OTransmit data channel
TXD0 OTransmit data channel
TXCK ITransmit data bit clock (4.8kHz.)
FMEN IEncoder frame flag (Active High)
RXD3 IReceive data channel
RXD2 IReceive data channel
RXD1 IReceive data channel
RXD0 IReceive data channel
RXCK IReceive data bit clock (4.8 kHz)
FMDE IDecoder frame flag (Active High)
VFRO OAnalog speech output signal
VRXI IAnalog speech input signal
RUN ORun Status Signal (Active High)
RESX OInternal Reset Status (Active Low)
DINRS IReset Signal (Active High)
VAD IVoice/Silence Detection Enable (Active Low)
DTMF_DAT ODTMF Tone Data
DTMF_DET ODTMF Tone Detected Flag (Active High)
GO IEncoder Voice Mode (Active High)

Section 6 –VC-20™ATC-10b Vocoder Board Advanced Features
VC-20ATC-10b Vocoder Board User’s Manual
page 8
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3.4 VC-20-ATC-10b Connector Signals
TXD3-0 TXD3-0are the voice data signals from the VC-20™ -ATC-10b encoder. These
signals changes state on each rising edge of TXCK. The 96 voice bits of each 20 ms
voice frame are transmitted in 24 TXCK cycles (TXCK = 9.6 kHz), resulting in an
effective data rate of 4800 bps. The first TXCK cycle of each frame is setup to allow the
VC-20™ -ATC-10b to operate in loopback mode (the decoder reads the first 4-bit
word as a control word). The first TXCK word contains 0000 binary, and then the next
24 TXCK cycles contain the 96 voice bits.
TXCK This is the encoder data clock which controls the transfer of the channel data out of the
encoder. This signal must be 9.6 kHz +/-.05%. TXD, FMEN, GO, and RUN are
synchronous with the rising edge of this clock signal to within 500 ns.
RXD3-0 RXD3-0 are the voice data signals input to the VC-20™ -ATC-10b decoder. These
signals are each clocked into the VC-20-ATC-10b on each falling edge of RXCK. The
96 voice bits plus 4 control bits of each 20ms voice frame are input in the first 25 RXCK
cycles (RXCK = 9.6 kHz). The first RXCK cycle contains a 4-bit control word, and the
remaining 24 RXCK cycles contain the voice bits, resulting in an effective data rate of 4.8
kbps. The four bits of the control word are organized as follows: RXD3 = LOST,
RXD2 = PARAMINIT, RXD1 = DESLNCE, and RXD0 is not currently used. LOST
signifies a lost frame of data (active high), PARAMINIT re-initializes the voice coder
parameters (active high), and DESLNCE signifies a frame of silence (active high).
RXCK This is the decoder symbol clock which controls the transfer of the channel data into the
decoder. This signal must be 9.6 kHz +/-.05%. RXD3-0, FMDE, and DESLNCE are
synchronous with the rising edge of this clock signal to within 500 ns.
FMEN This is the encoder frame flag which identifies the frame boundary of the
channel output data. FMEN must be active for one clock period of TXCK
every 20 ms.
FMDE This is the decoder frame flag which identifies the frame boundary of the channel input
data. FMDE must be active for one clock period of RXCK every 20 ms.
VRXI VFXI is the analog speech input which is filtered with a 100 Hz. -3600 Hz. bandpass
filter and then input to the encoder via a 16 bit linear codec. In order to avoid clipping
VRXI must not exceed +/-1.5 volts.

Section 6 –VC-20™ ATC-10b Vocoder Board Advanced Features
VC-20ATC-10b Vocoder Board User’s Manual page 9
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VFRO VFRO is the analog speech output produced by passing the decoder output through a 16
bit linear codec. VFRO has an analog bandwidth of 100 Hz. -3600 Hz., and it is
constrained to be within +/-1.5 volts.
RUN RUN is a status signal that signifies that the VC-20™ -ATC-10b is encoding and
decoding speech. This signal drives the green LED. Each data frame is divided into an
encoder window and a decoder window. The RUN signal is active within each
respective window when the VC-20™ -ATC-10b is encoding or decoding speech (see
figure 6). RUN is synchronous with TXCK.
RESX RESX is the reset status output signal. It is active when the VC-20-MTR is being reset.
The VC-20™ -ATC-10b is reset under three conditions: during power-up, as a result of
DINRS being asserted, or as a result of a Watch-Dog Timer reset. This signal is an
active low output. RESX is the VC-20™ -ATC-10b 's actual hard-reset signal;
whereas, RESET is a software flag that is synchronous with TXCK.
DINRS DINRS is a VC-20™ -ATC-10b reset signal. An active high level on DINRS for a
duration of at least 300ns will reset the VC-20™ -ATC-10b. DINRS will generate
RESX and RESET. The VC-20™ -ATC-10b will pull this signal to its inactive state
(low) when it is not being driven by an external source (it may be left unconnected if not
being used).
VAD The VAD signal must be held low to enable the onboard Voice/Silence detection and
comfort noise generation. This signal is sampled on the falling edge of the first clock
cycle of each 20 ms encoder frame. If left unconnected, this signal is pulled internally to
the disabled state (high).
DTMF_DET The DTMF_DET flag is activated by the encoder if it detects a DTMF tone on VRXI.
The DTMF_DET is brought high on a rising edge of TXCK and held high for four clock
cycles. During this time the DTMF data is output on DTMF_DAT. The DTMF_DET
flag is only output once for each continuous DTMF tone that is detected. DTMF_DET
can only be active during the first four clock cycles of a 20 ms data frame.
DTMF_DAT If the VC-20™ -ATC-10b detects a DTMF tone, it outputs four bits of data identifying
the tone on the DTMF_DAT signal (see Section 3.7). The data is output during the four
clock cycles when DTMF_DET is high. The data is synchronous with the rising edge of
TXCK. This signal should be ignored when DTMF_DET is inactive.

Section 6 –VC-20™ATC-10b Vocoder Board Advanced Features
VC-20ATC-10b Vocoder Board User’s Manual
page 10
The Speech Compression Specialists
D
IGITAL
V
OICE
S
YSTEMS,
I
NC.
GO The GO signal must be active to place the encoder in voice mode. This signal is sampled
every 20 ms when FMEN is high. If this signal is active then the encoder outputs voice
data on TXD during the next 20 ms frame. Otherwise, if this signal is inactive then the
encoder resets itself internally and outputs a silence frame on TXD during the next 20 ms
frame. The relationship between FMEN, GO and TXD is shown in Figure 1. If left
unconnected, GO is pulled to its active state (high).
TXD
Silence
Frames
Voice
Frames
GO
FMEN
Voice
Frames Voice Frames
Silence
Frames
Figure 1: Voice/Silence Mode Selection
GND, AGND GND is the digital ground signal and AGND is the analog ground signal. These signals
are connected on the VC-20™ -ATC-10b.
3.5 Silence Frame Designation
The VC-20™ -ATC-10b encoder continually outputs a silence frame whenever the GO
signal is inactive (see Figure 1). If the decoder receives this signal it outputs a low level (-
75 dBm) noise signal on VFRO