Does jammer blocks one frequency or many bands simultaneously?

Hello everybody! I have not much knowledge about jammers so I want to know how they work – are they block only one frequency band or few at the same time?

RTL 5 Minutes (Registration) Mileage Tax Trucks use scrambler not to payRTL 5 Minutes (Registration) To avoid paying the mileage tax, some truck drivers over 3.5 tons have a GPS jammer . The vehicle then becomes stealthy, so to speak. Anonymously, a foreign carrier spoke in the RTL info 13h.and more »

dh.beTimetric mileage: Road drivers use a GPS jammer to avoid paydh.beSome truck drivers use a jammer gps to avoid paying the kilometric tax, reveals RTL-TVi Monday. This device, sold on the internet, prevents normal operation of the OBU, which calculates the kilometers traveled … and more “.

The most popular combinations of jammed frequency ranges are those within one band, for example GSM frequencies like GSM850, GSM900, GSM1800 and GSM1900 are no longer blocked separately but together and by means of one signal jammer. Yet more and more different frequencies are added to the jamming list now and they have created new jammer types like WiFi/Bluetooth/3G/GSM jammer, 4G/LoJack/XM radio jammer or even multifrequency desktop jammer which jammed frequencies are tuned in advance before the purchase.

As you can see, modern technologies are not standing still and constantly advancing to treat us with new impressive features.