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Recommendation
ITU-R M.2034
(02/2013)
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Telegraphic alphabet for data communication
by phase shift
keying at 31 Bd in the amateur and amateur-satellite services |
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M Series
Mobile, radiodetermination, amateur
and related satellite services
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The role of the Radiocommunication Sector is to ensure
the rational, equitable, efficient and economical use of the radio-frequency
spectrum by all radiocommunication services, including satellite services, and
carry out studies without limit of frequency range on the basis of which
Recommendations are adopted.
The
regulatory and policy functions of the Radiocommunication Sector are performed
by World and Regional Radiocommunication Conferences and Radiocommunication
Assemblies supported by Study Groups.
Policy on Intellectual Property Right (IPR)
ITU-R policy on IPR is
described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in
Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent
statements and licensing declarations by patent holders are available from http://www.itu.int/ITU-R/go/patents/en where the Guidelines for
Implementation of the Common Patent Policy for ITU‑T/ITU‑R/ISO/IEC and the
ITU-R patent information database can also be found.
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Series of ITU-R
Recommendations
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Series
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Title
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BO
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Satellite delivery
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BR
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Recording
for production, archival and play-out; film for television
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BS
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Broadcasting service (sound)
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BT
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Broadcasting
service (television)
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F
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Fixed service
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M
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Mobile, radiodetermination, amateur and related satellite services
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P
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Radiowave propagation
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RA
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Radio astronomy
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RS
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Remote sensing systems
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S
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Fixed-satellite service
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SA
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Space applications and meteorology
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SF
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Frequency sharing and coordination between
fixed-satellite and fixed service systems
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SM
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Spectrum management
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SNG
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Satellite news gathering
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TF
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Time signals and frequency standards
emissions
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V
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Vocabulary and related subjects
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Note: This ITU-R
Recommendation was approved in English under the procedure detailed in
Resolution ITU-R 1.
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Electronic Publication
Geneva, 2013
All
rights reserved. No part of this publication may be reproduced, by any means whatsoever,
without written permission of ITU.
Telegraphic alphabet
for data communication by phase shift keying
at 31 Bd in the amateur and amateur-satellite services
at 31 Bd in the amateur and amateur-satellite services
(Question ITU-R 48-6/5)
Scope
This Recommendation
establishes a telegraphic alphabet and transmission protocols for phase shift
keying at 31 Bd in the amateur and amateur-satellite services.
The ITU
Radiocommunication Assembly,
considering
a) that phase shift keying at a data rate
of 31 Bd has become a predominant transmission mode in the amateur and
amateur-satellite services;
b) that phase shift keying at 31 Bd
utilizes a telegraphic alphabet, commonly called “Varicode”, optimized for the
English language, in which more frequently used characters occupy fewer bits;
c) that telegraphic alphabets should be
documented and updated from time to time to meet the needs of
radiocommunication services,
recommends
1 that the Annex should be
used to define Varicode characters and their applications in the amateur and
amateur-satellite services.
Annex
1 Introduction
PSK‑31 is a digital
communication mode which is intended for live keyboard-to-keyboard
conversations, similar to radioteletype. Its data rate is 31.25 Bd (about
50 words per minute), and its narrow bandwidth (approximately
60 Hz at –26 dB) reduces its susceptibility to noise. PSK‑31’s ITU
emission designator is 60H0J2B. It uses either BPSK modulation without error
correction or QPSK modulation with error correction (convolutional encoding and
Viterbi decoding). In order to minimize occupied bandwidth, the output is
cosine-filtered before reaching the transmitter audio input. PSK‑31 is readily
monitored and the most popular implementations use DSP software running on a
computer soundcard.
Each transmission has
a preamble, an idle signal of continuous zeroes corresponding to continuous
phase reversals at the symbol rate of 31.25 reversals/second, and a
postamble, continuous unmodulated carrier representing a series of logical
ones. The absence of phase reversals squelches the decoder.
While a symbol rate of
31.25 Bd is typical of most amateur service use, the symbol rate can be
varied in direct proportion to the frequency of phase reversals. Transmissions
at symbol rates as high as 125 Bd have been achieved.
2 Varicode characters
Different characters
are represented by a variable-length combination of bits called Varicode.
Because shorter bit-lengths are used for the more common letters in the English
language, Varicode improves efficiency in terms of the average character
duration. Varicode is also self-synchronizing. No separate process is needed to
define where one character ends and the next begins since the pattern used to
represent a gap between two characters (at least two consecutive zeroes) never
occurs in a character. Because no Varicode characters can begin or end with a
zero (0), the shortest character is a single one (1) by itself. The next is 11,
then 101, 111, 1011, and 1101, but not 10, 100, or 1000 (because they end
with zeroes), and not 1001 (since it contains two consecutive zeros).
This scheme generates the 128-character ASCII set with ten bits. The
encoding philosophy, however, accommodates longer bit sequences which allow for
additional characters, e.g. accented characters.
The Varicode character set is shown below. The codes are transmitted
left bit first, with 0 representing a phase reversal on BPSK and 1 representing
a steady carrier. A minimum of two zeros is inserted between characters.
Some implementations may not handle all the codes below 32. Note that the lower
case letters have the shortest patterns and so are the fastest to transmit.
The varicode character
set control characters
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Varicode
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Abbreviation
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Description
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1010101011
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NUL
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Null character
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1011011011
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SOH
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Start of Header
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1011101101
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STX
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Start of Text
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1101110111
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ETX
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End of Text
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1011101011
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EOT
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End of Transmission
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1101011111
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ENQ
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Enquiry
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1011101111
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ACK
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Acknowledgment
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1011111101
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BEL
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Bell
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1011111111
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BS
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Backspace
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11101111
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HT
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Horizontal Tab
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11101
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LF
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Line feed
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1101101111
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VT
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Vertical Tab
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1011011101
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FF
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Form feed
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11111
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CR
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Carriage return
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1101110101
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SO
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Shift Out
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1110101011
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SI
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Shift In
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1011110111
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DLE
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Data Link Escape
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1011110101
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DC1
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Device Control 1 (XON)
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1110101101
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DC2
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Device Control 2
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1110101111
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DC3
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Device Control 3 (XOFF)
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1101011011
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DC4
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Device Control 4
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1101101011
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NAK
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Negative Acknowledgement
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1101101101
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SYN
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Synchronous Idle
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1101010111
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ETB
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End of Trans. Block
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1101111011
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CAN
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Cancel
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1101111101
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EM
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End of Medium
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1110110111
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SUB
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Substitute
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1101010101
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ESC
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Escape
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1101011101
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FS
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File Separator
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1110111011
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GS
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Group Separator
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1011111011
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RS
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Record Separator
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1101111111
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US
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Unit Separator
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1110110101
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DEL
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Delete
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Printable characters
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Varicode
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Glyph
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Varicode
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Glyph
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Varicode
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Glyph
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1
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SP
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1010111101
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@
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1011011111
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`
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111111111
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!
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1111101
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A
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1011
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a
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101011111
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"
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11101011
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B
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1011111
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b
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111110101
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#
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10101101
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C
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101111
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c
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111011011
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$
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10110101
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D
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101101
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d
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1011010101
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%
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1110111
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E
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11
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e
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1010111011
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&
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11011011
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F
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111101
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f
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101111111
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'
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11111101
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G
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1011011
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g
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11111011
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(
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101010101
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H
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101011
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h
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11110111
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)
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1111111
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I
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1101
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i
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101101111
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*
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111111101
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J
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111101011
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j
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111011111
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+
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101111101
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K
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10111111
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k
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1110101
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,
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11010111
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L
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11011
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l
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110101
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-
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10111011
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M
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111011
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m
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1010111
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.
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11011101
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N
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1111
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n
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110101111
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/
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10101011
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O
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111
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o
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10110111
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0
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11010101
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P
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111111
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p
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10111101
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1
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111011101
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Q
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110111111
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q
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11101101
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2
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10101111
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R
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10101
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r
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11111111
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3
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1101111
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S
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10111
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s
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101110111
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4
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1101101
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T
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101
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t
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101011011
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5
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101010111
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U
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110111
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u
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101101011
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6
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110110101
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V
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1111011
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v
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110101101
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7
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101011101
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W
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1101011
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w
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110101011
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8
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101110101
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X
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11011111
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x
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110110111
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9
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101111011
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Y
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1011101
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y
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11110101
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:
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1010101101
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Z
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111010101
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z
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110111101
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;
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111110111
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[
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1010110111
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{
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111101101
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<
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111101111
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\
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110111011
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1010101
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=
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111111011
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]
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1010110101
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}
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111010111
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>
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1010111111
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^
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1011010111
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~
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1010101111
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?
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101101101
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_
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