.. Permission is granted to copy, distribute and/or modify this
.. document under the terms of the GNU Free Documentation License,
.. Version 1.1 or any later version published by the Free Software
.. Foundation, with no Invariant Sections, no Front-Cover Texts
.. and no Back-Cover Texts. A copy of the license is included at
.. Documentation/userspace-api/media/fdl-appendix.rst.
..
.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections

.. _FE_SET_TONE:

*****************
ioctl FE_SET_TONE
*****************

Name
====

FE_SET_TONE - Sets/resets the generation of the continuous 22kHz tone.


Synopsis
========

.. c:function:: int ioctl( int fd, FE_SET_TONE, enum fe_sec_tone_mode tone )
    :name: FE_SET_TONE


Arguments
=========

``fd``
    File descriptor returned by :ref:`open() <frontend_f_open>`.

``tone``
    an integer enumered value described at :c:type:`fe_sec_tone_mode`


Description
===========

This ioctl is used to set the generation of the continuous 22kHz tone.
This call requires read/write permissions.

Usually, satellite antenna subsystems require that the digital TV device
to send a 22kHz tone in order to select between high/low band on some
dual-band LNBf. It is also used to send signals to DiSEqC equipment, but
this is done using the DiSEqC ioctls.

.. attention:: If more than one device is connected to the same antenna,
   setting a tone may interfere on other devices, as they may lose the
   capability of selecting the band. So, it is recommended that applications
   would change to SEC_TONE_OFF when the device is not used.


Return Value
============

On success 0 is returned.

On error -1 is returned, and the ``errno`` variable is set
appropriately.

Generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.