In fact, they have existed in different identities for many years. The location of the signal jammer can be far away from the radio waves.
Today's testing equipment uses signal jammers to ensure that candidates will not cheat in the exam. They can also be used in operating rooms to prevent certain signals from affecting the equipment.
The private sector uses them regularly (if not permanently) to prevent data attacks and hacking. We even heard that jammers are used in churches to prevent the use of mobile phones.
The technology behind signal jammer can block almost any type of reception (from mobile phones to wifi to radio).
Essentially, if someone tries to prevent others from stealing data, they must stop the signals floating between their technologies.