Some phones are quad band, i.e. 4. This is a 2 band jammer. Some phones can work around it, others can't. When I've been playing around with it it is possible to jam most phones whilst they're in the middle of a call.
Right, just tested mine:
- Code: Select all | TOGGLE FULL SIZE
Program #1 of 1
VCO 1: 1805 -> 1880 (30, 254)
VCO 2: 925 -> 960 (30, 254)
(Think mine's having problems, no way 1880MHz is 254, it would be more like 2500MHz...)
Now I'm in the UK so those are the UK bands for GSM/WCDMA and I just made a call to 1234 (speaking clock), connected fine, then I turn the jammer on, and the call is dropped. I've got a modern smart phone which is quad band so despite that, it definitely works (although I'm a bit worried about those values of 254 :? ).
Note the "non plus ultra new design" is purely a streamlining of the old WB design wit ha few little tweaks (VCOpower select, more common parts etc)