217 lines
7.3 KiB
Groff
217 lines
7.3 KiB
Groff
.\" Hey, EMACS: -*- nroff -*-
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.\" First parameter, NAME, should be all caps
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.\" Second parameter, SECTION, should be 1-8, maybe w/ subsection
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.\" other parameters are allowed: see man(7), man(1)
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.TH MINIMODEM 1 "August 19, 2012"
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.\" Please adjust this date whenever revising the manpage.
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.\"
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.\" Some roff macros, for reference:
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.\" for manpage-specific macros, see man(7)
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.SH NAME
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minimodem \- software audio Bell-type or RTTY FSK modem
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.SH SYNOPSIS
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.B minimodem --tx
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.RI [ options ]
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.I {baudmode}
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.br
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.B minimodem --rx
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.RI [ options ]
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.I {baudmode}
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.SH DESCRIPTION
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.B minimodem
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is a command-line program which generates (or decodes) audio
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modem tones at any specified baud rate, emulating an old Bell-type or
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radio-teletype FSK modem. The tones can be played to (or recorded from)
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the system audio (PulseAudio or ALSA) or to an audio file.
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.PP
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.B minimodem
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can be used to transfer data between nearby computers using an audio
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cable (or just via sound waves), or between remote computers using radio,
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telephone, or another audio communications medium.
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.SH "TX/RX MODE"
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.TP
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.B \-t, \-\-tx, \-\-transmit, \-\-write
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transmit mode: generate audio tones
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.TP
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.B \-r, \-\-rx, \-\-receive, \-\-read
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receive mode: decode audio tones
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.SH {baudmode}
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The required \fI{baudmode}\fR parameter may be any floating-point value to
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specify a baud rate, or any of the special keywords listed below.
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The \fI{baudmode}\fR also implies certain other parameter defaults
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depending on the rate, including standard (or at least reasonable)
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default mark and space tone frequencies.
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.TP
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.B {any floating point value N}
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: Bell202-style at N bps \-\-ascii
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.TP
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.B 1200
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: Bell202 1200 bps \-\-ascii
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.TP
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.B 300
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: Bell103 300 bps \-\-ascii
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.TP
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.B rtty
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: RTTY 45.45 bps \-\-baudot \-\-stopbits 1.5
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.TP
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.B same
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: SAME 520.83 bps \-\-startbits 0 \-\-stopbits 0 \-\-sync-byte 0xAB
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.br
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NOAA Specific Area Message Encoding (SAME) protocol
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.TP
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.B callerid
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: Bell202 1200 bps Caller-ID (MDMF or SDMF) protocol
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.SH OPTIONS
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.TP
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.B \-a, \-\-auto-carrier
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Automatically detect mark and space frequences from carrier.
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.TP
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.B \-i, \-\-inverted
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Invert the mark and space frequencies (applies whether the
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frequencies are defaults, discovered by \-\-auto-carrier,
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or specified manually).
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.TP
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.B \-c, \-\-confidence min-confidence-threshold
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Set receive confidence minimum threshold (default 1.5).
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The "confidence" value is a metric based primarily on
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the SNR (signal-to-noise ratio) of the received signal.
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This value acts as an FSK decoder "squelch" control.
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Increase to accept only very clean signals (up to INFINITY, but
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a value around 5.0 is more practical). Decrease to accept partial
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decoding of noisy signals (down to a minimum value of 1.0).
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(This option applies to \-\-rx mode only).
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.B \-l, \-\-limit max-confidence-search-limit
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Set receive confidence maximum search limit (default 2.3).
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The "confidence" value is as described above.
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This value acts as a performance vs. analysis quality control.
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Increase (up to INFINITY) for a more pedantic analysis
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and higher CPU usage. Decrease (down to the min-confidence-threshold)
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for a sloppier analysis, with lower CPU usage.
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(This option applies to \-\-rx mode only).
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.TP
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.B \-8, \-\-ascii
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ASCII 8\-N\-1
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.TP
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.B \-5, \-\-baudot
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Baudot 5\-N\-1.5
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.TP
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.B \-f, \-\-file filename.wav
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encode or decode an audio file (extension sets audio format)
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.TP
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.B \-b, \-\-bandwidth {rx_bandwidth}
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.TP
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.B \-v, \-\-volume {tx_amplitude or 'E'}
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Sets the generated signal amplitude (default is 1.0). As a special case
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useful for testing, the value 'E' sets the amplitude to the very small value
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FLT_EPSILON. (This option applies to \-\-tx mode only).
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.TP
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.B \-M, \-\-mark {mark_freq}
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.TP
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.B \-S, \-\-space {space_freq}
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.TP
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.B \-\-startbits {n}
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Sets the number of start bits (default is 1 for most baudmodes).
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.TP
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.B \-\-stopbits {n.n}
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Sets the number of stop bits (default is 1.0 for most baudmodes).
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.TP
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.B \-\-sync-byte {0xXX}
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If this option is used, initial carrier acquisition will be suppressed
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until after one or more consecutive data frame(s) containing this value
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are received. This can be used to synchronize the stream for protocols
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which include a fixed preamble byte.
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(This option applies to \-\-rx mode only).
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.TP
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.B \-q, \-\-quiet
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Do not report CARRIER / NOCARRIER or signal analysis metrics.
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.TP
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.B \-R, \-\-samplerate {rate}
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Set the audio sample rate (default rate is 48000 Hz).
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.TP
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.B \-A, \-\-alsa[={plughw:X,Y | X,Y | X }]
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Use ALSA as the audio output system instead of the default
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PulseAudio (depending on build configuration options). The ALSA
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device alias "default" is used, if a specific device is not specified.
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For example, the following options all select ALSA device #1, sub-device #0:
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\-\-alsa=plughw:1,0 \-\-alsa=1,0 \-A1
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.TP
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.B \-\-lut={tx_sin_table_len}
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Minimodem uses a precomputed sine wave lookup table of 1024 elements,
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or the size specified here. Use \-\-lut=0 to disable the use of
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the sine wave lookup table. (This option applies to \-\-tx mode only).
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.TP
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.B \-\-float-samples
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Generate 32-bit floating-point format audio samples, instead of the
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default 16-bit signed integer format (applies to \-\-tx mode only;
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\-\-rx mode always uses 32-bit floating-point).
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.TP
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.B \-\-rx-one
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Quit after the first carrier/no-carrier event (applies to \-\-rx mode only).
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.TP
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.B \-\-binary-output
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Print received data bits as raw binary output using characters '0' and '1'.
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The bits are printed in the order they are received. Framing bits (start
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and stop bits) are omitted from the output.
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(This option applies to \-\-rx mode only).
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.TP
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.B \-\-print-filter
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Filter the received text output, replacing any "non-printable" bytes
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with a '.' character.
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(This option applies to \-\-rx mode only).
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.TP
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.B \-\-benchmarks
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Run and report internal performance tests (all other flags are ignored).
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.TP
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.B \-V, \-\-version
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print program version
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.SH EXAMPLES
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.TP
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.B minimodem --tx 100
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Transmit 100 baud tones from one computer ...
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.TP
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.B minimodem --rx 100
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and receive 100 baud tones on another nearby computer.
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.TP
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.B minimodem --rx -a rtty
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Decode amateur radio RTTY signals (listen near 14.085 MHz).
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.TP
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.B minimodem --rx same
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Decode NOAA SAME protocol emergency alert transmissions, e.g.
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.br
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http://en.wikipedia.org/wiki/Specific_Area_Message_Encoding
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.TP
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.B minimodem --tx 0.5
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Experiment with very low baud rates (works in noisy conditions).
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.TP
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.B minimodem --tx 12000
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Experiment with very high baud rates (works with audio files).
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.SH NOTES
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.B minimodem
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does not decode AX.25 framed packets.
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.PP
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.B minimodem
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does not support modem control ("AT") commands, nor does it produce
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DTMF telephone dialing tones.
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.SH VERSION
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This page documents
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.B minimodem
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version @PACKAGE_VERSION@.
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The latest version is available at <http://www.whence.com/minimodem>.
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.SH AUTHOR
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.B minimodem
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was written by Kamal Mostafa <kamal@whence.com>.
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.SH COPYRIGHT
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Copyright \(co 2011-2012 by Kamal Mostafa <kamal@whence.com>.
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
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.br
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This is free software: you are free to change and redistribute it.
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There is NO WARRANTY, to the extent permitted by law.
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