Signal jammer vs scrambler
Jammer and Scrambler serve very different purposes.

Jammer generates interference, which inhibits the ability to receive the signal.
Alice transmits a signal for Bob to receive.  Oscar transmits a jamming signal, which interferes with the transmission.  Bob sees a reduced SNR at his receiver.  Bob's ability to receive Alice's signal is suppressed.

Scrambler is similar to encryption of the signal.  There's a also a type of device called Descrambler, which converts the signal to an intelligible form.
Alice transmits a signal for Bob to receive.  Eve wants to eavesdrop on the signal and obtain its content.  To prevent eavesdropping, Alice scrambles the signal.  By agreement with Alice, Bob has an appropriate descrambler, so he can convert the signal to an intelligible form.  Eve doesn't have an agreement with Alice, and she doesn't have an appropriate descrambler.  Eve can not obtain the content of the signal.