Provided by: minimodem_0.19-1_amd64 bug


       minimodem - general-purpose software audio FSK modem


       minimodem --tx [options] {baudmode}
       minimodem --rx [options] {baudmode}


       Minimodem  is a command-line program which decodes (or generates) audio modem tones at any
       specified baud rate, using various framing protocols.  It acts a general-purpose  software
       FSK  modem,  and  includes  support  for  various  standard FSK protocols such as Bell103,
       Bell202, RTTY, NOAA SAME, and Caller-ID.

       Minimodem can play and capture audio modem tones in real-time via the system audio device,
       or in batched mode via audio files.

       Minimodem  can  be used to transfer data between nearby computers using an audio cable (or
       just via sound waves), or between remote computers  using  radio,  telephone,  or  another
       audio communications medium.


       -t, --tx, --transmit, --write
              transmit mode: generate audio tones

       -r, --rx, --receive, --read
              receive mode: decode audio tones


       The  required {baudmode} parameter may be any floating-point value to specify a baud rate,
       or any of the special keywords listed below.  The {baudmode} also  implies  certain  other
       parameter  defaults  depending  on  the  rate, including standard (or at least reasonable)
       default mark and space tone frequencies.

       {any floating point value N}
              : Bell202-style at N bps --ascii

       1200   : Bell202 1200 bps --ascii

       300    : Bell103 300 bps --ascii

       rtty   : RTTY 45.45 bps --baudot --stopbits 1.5

       same   : SAME 520.83 bps --startbits 0 --stopbits 0 --sync-byte 0xAB
                   NOAA Specific Area Message Encoding (SAME) protocol

              : Bell202 1200 bps Caller-ID (MDMF or SDMF) protocol


       -a, --auto-carrier
              Automatically detect mark and space frequences from carrier.

       -i, --inverted
              Invert the  mark  and  space  frequencies  (applies  whether  the  frequencies  are
              defaults, discovered by --auto-carrier, or specified manually).

       -c, --confidence min-confidence-threshold
              Set  receive confidence minimum threshold (default 1.5).  The "confidence" value is
              a metric based primarily on the SNR (signal-to-noise ratio) of the received signal.
              This  value acts as an FSK decoder "squelch" control.  Increase to accept only very
              clean signals (up to INFINITY, but a value around 5.0 is more practical).  Decrease
              to  accept  partial  decoding  of  noisy  signals (down to a minimum value of 1.0).
              (This option applies to --rx mode only).  -l,  --limit  max-confidence-search-limit
              Set  receive confidence maximum search limit (default 2.3).  The "confidence" value
              is as described above.  This value acts  as  a  performance  vs.  analysis  quality
              control.   Increase  (up  to  INFINITY) for a more pedantic analysis and higher CPU
              usage.  Decrease (down to the min-confidence-threshold) for  a  sloppier  analysis,
              with lower CPU usage.  (This option applies to --rx mode only).

       -8, --ascii
              ASCII  8-N-1

       -5, --baudot
              Baudot 5-N-1.5

       -f, --file filename.wav
              encode or decode an audio file (extension sets audio format)

       -b, --bandwidth {rx_bandwidth}

       -v, --volume {tx_amplitude or 'E'}
              Sets the generated signal amplitude (default is 1.0).  As a special case useful for
              testing, the value 'E' sets the amplitude to  the  very  small  value  FLT_EPSILON.
              (This option applies to --tx mode only).

       -M, --mark {mark_freq}

       -S, --space {space_freq}

       --startbits {n}
              Sets the number of start bits (default is 1 for most baudmodes).

       --stopbits {n.n}
              Sets the number of stop bits (default is 1.0 for most baudmodes).

       --sync-byte {0xXX}
              If  this option is used, initial carrier acquisition will be suppressed until after
              one or more consecutive data frame(s) containing this value are received.  This can
              be  used  to  synchronize  the  stream for protocols which include a fixed preamble
              byte.  (This option applies to --rx mode only).

       -q, --quiet
              Do not report CARRIER / NOCARRIER or signal analysis metrics.

       -R, --samplerate {rate}
              Set the audio sample rate (default rate is 48000 Hz).

       -A, --alsa[={plughw:X,Y | X,Y | X }]
              Use ALSA as the audio output system instead of the default PulseAudio (depending on
              build  configuration  options).   The  ALSA  device  alias  "default" is used, if a
              specific device is not specified.  For example, the following  options  all  select
              ALSA device #1, sub-device #0:
               --alsa=plughw:1,0  --alsa=1,0  -A1

              Minimodem  uses  a precomputed sine wave lookup table of 1024 elements, or the size
              specified here.  Use --lut=0 to disable the use of  the  sine  wave  lookup  table.
              (This option applies to --tx mode only).

              Generate  32-bit floating-point format audio samples, instead of the default 16-bit
              signed integer format (applies to --tx mode only;  --rx  mode  always  uses  32-bit

              Quit after the first carrier/no-carrier event (applies to --rx mode only).

              Print  received  data  bits as raw binary output using characters '0' and '1'.  The
              bits are printed in the order they are received.   Framing  bits  (start  and  stop
              bits) are omitted from the output.  (This option applies to --rx mode only).

              Filter  the  received  text  output, replacing any "non-printable" bytes with a '.'
              character.  (This option applies to --rx mode only).

              Run and report internal performance tests (all other flags are ignored).

       -V, --version
              print program version


       minimodem --tx 100
              Transmit 100 baud tones from one computer ...

       minimodem --rx 100
              and receive 100 baud tones on another nearby computer.

       minimodem --rx -a rtty
              Decode amateur radio RTTY signals (listen near 14.085 MHz).

       minimodem --rx same
              Decode NOAA SAME protocol emergency alert transmissions, e.g.

       minimodem --tx 0.5
              Experiment with very low baud rates (works in noisy conditions).

       minimodem --tx 12000
              Experiment with very high baud rates (works with audio files).


       minimodem does not decode AX.25 framed packets.

       minimodem does not support modem  control  ("AT")  commands,  nor  does  it  produce  DTMF
       telephone dialing tones.


       This  page  documents  minimodem  version  0.19.   The  latest  version  is  available  at


       minimodem was written by Kamal Mostafa <>.


       Copyright © 2011-2013 by  Kamal  Mostafa  <>.   License  GPLv3+:  GNU  GPL
       version 3 or later <>.
       This  is free software: you are free to change and redistribute it.  There is NO WARRANTY,
       to the extent permitted by law.

                                          June 10, 2013                              MINIMODEM(1)