Allows to specify URL param which will not be checked by redirector. This setting can be used in case of disabled URL signed protection. In this way you can forbid changing of download settings specified for account or domain.
Default download speed for account has been set up as 120% of video bitrate.
There is a link
User can specify any necessary speed in case of disabled URL signed protection.
But changing of speed setting won't work if you specified 'speed' in param_block setting