This plugin wraps the seznam.cz Captcha API.
Additional protection by checking online spam databases and blacklists could be activated in the configuration. Currently StopForumSpam, SpamBusted, BotScout, SpamHaus, Sorbs, SpamCop and project HoneyPot are supported. There is also possibility to manually enter IP blacklist and/or whitelist.
Since version 1.2.0, there is option to disable visual CAPTCHA control, and use just additional protection.
n3t Seznam Captcha is standard Joomla Captcha plugin. It means, first you have to enable the plugin, second tell Joomla to use this plugin. This can be done either in Global Configuration (Default Captcha), or in component itself (for example in users component configuration field Captcha).
Captcha has to be supported in component you use for registration. Standard Joomla registration support this, however if you use another component, some of them doesn't need to support standard Joomla Captcha plugins.
And finally, it has to be supported by template also, if nothing from above works, try to switch to one of default templates.
CAPTCHA solution is hosted by Czech service provider, this plugin only wrapps its functionality in Joomla. So the english audio chalenge is something what cannot be influenced by me. If provider will support english audio in the future, surely this plugin will provided also.
When i installed it, i noticed the plugin to not force the required class to be validated by the form validator class. So i sent suggestions to the author and got immediate response combined with a prompt help offer and the plugin was also immediately udpated overnight.
I can hightly recommend this extension and its developer.
Thanks a bunch again to the author.