The size of the gsm jammer in the classroom will vary depending on the type of device. If you have a strong jammer, the antenna will be located outside to provide better coverage and coverage. Another advantage of adjustable units is the ability to "turn down" so they do not block adjacent areas.
It can block all types of cell phone signals, and you can call, receive and send messages, and get online. This means that you must shield the following frequency ranges: CDMA / GSM / DCS / PHS / TD-SCDMA / WCDMA / CDMA2000; the effective protection distance must reach 20 meters; the price is reasonable and the quality period is three years or more. Schools use cell phone jammmer only during exams, and turn them off when you exit.
For schools, buy GSM jammers are very cheap and have limited range, which can be very certain. This means that the "closed area" can also be well controlled, with no pedestrians or neighbors affected. The "no cellphone zone" is in class or school. "