To prevent communications during meeting,in examination with this portable GSM,3G cellphone jammer is best option,just need power on the device then it will start working,in 1 minute all GSM,3G signal will disable,to stop all cellphone communication.
mobile phone jammer also named as phone blocker or phone breakers, the mobile phone jammer are built in a high quality aluminium housing,use one jammer could be blocking phone call and sms message in a 12 x 12 feet room,with several mobile phone jammer in larger rooms or halls to jamming communications.
Use for blocking all mobile phone bands around the world in all countries including the new 3G networks.

Portable 3G,GSM Cellphone Jammer Features:
1, Portable cell phone jammer with built in battery
2, Support jam GPRS,GSM,DCS,CDMA,PDC,TDMA,PHS,PCS,IDEN,W-CDMA,UMTS
3, Effective range up to 20 meters
4, Built in battery support conitune working up to 2 hours
5, One switch to power on and automatic start working
6, With antenna to working for long range
7, Not will be jam GPS signal
Portable 3G,GSM Cellphone Jammer Specification:
1, Frequency:
A, TX frequency 851-960 MHz
B, TX frequency 1805-1880MHz or 1930-1990 MHz
C, Tx frequency 2100-2170MHz
2,Output Power:
Frequency(A): +25dBm / 300mW
Frequency(B): +25dBm / 300mW
Frequency(C): +25dBm / 300mW
3, Jamming range: 5~20 meters in radius
4, Built in 2600mah Li-battery
5, Working time: up to 2 hours
6, System compatible:
A, Analog (AMPS,TACS,NMT)
B, Digital (GPRS,GSM,DCS,CDMA,PDC,TDMA,PHS,PCS,IDEN,W-CDMA,UMTS)
7, With remote controller to power on or stop working
8, With 3 antennas
9,110(H)