Black to Black
Calling another black user is the most secure silent mobile call, the call is encrypted by the caller and decrypted by the receiver, making the call MiTM free. Security level 100%
Black to Out
Calling a regular non silent smartphone, will let you call from a random country of the world with a random phone number. Calling that number back by the receiver after the connection drops, will be impossible. Security level 100% (do not reveal personal information and your identity will be unknown by everyone except for the known call receiver).
Does not record any data. The BLACK system encrypts the contents of the conversations in total security leaving no traces, nor the possibility to record any data.