Mobile jammers were originally developed for law enforcement agencies and the military to interfere with the communications of criminals and terrorists. The bomb was dropped in Spain in March 2004, the bomb exploded in Bali in October 2002, and Jakarta in August 2003, relying on mobile phones to trigger explosives. According to reports, a mobile cell phone jammer prevented the assassination attempt on Pakistani President Musharraf in December 2003. But it can also be used illegally and improperly. On the more suspicious side of legitimacy, there are rumors that hotel chain disruptors are preventing any use of mobile phones for users and forcing them to use indoor phones at high prices.
In addition to mobile phone jammers (corresponding to GSM, 3G, 4G signals), there are GPS jammers that can block GPS signals. They can interfere with GPS trackers, GPS navigators, etc. Similarly, Bluetooth and WiFi jammers will interfere with wlan signals and accordingly block WiFi devices, such as wireless networks. UHF/VHF bands (including LoJack) and XM satellite jammers can interfere with devices that use these signals. Like some devices (such as fixed telephones), they will use lines, so they will not be affected by any signal interference. Therefore, even if you use a GSM/3G blocker, your landline phone is fine.