Compared with other jammers, mobile cell phone jammer will not send interference signals on the control channel. When the device is located in a designated “quiet” area, it will act as a “detector.” It has a unique identification number used to communicate with cellular base stations. When a “B” type device detects the presence of a mobile phone in a quiet room; “filtering” (ie, authorization to prevent call establishment) is performed by the software at the base station. When the base station transmits a signal to the target user, after detecting the presence of the signal and the target user at the same time, the device sends a signal to the base station to inform the target user that the target user is in a “quiet” room. Therefore, do not establish communication. If the user subscribes to the voice mail service, the mail can be forwarded to the user’s voice mailbox. The process of identifying and discontinuing call setup takes place in the time interval normally reserved for signaling and handshaking. For “emergency users”, smart detector devices provide emergency status to certain users. These users must pre-register their phone numbers with the service provider. When an incoming call is made, the detector will recognize the number and establish the call within a certain maximum duration (for example, two minutes). It also allows emergency users to make current calls. The system can also identify and allow all emergency calls forwarded to “911”. It should be noted that the “B” type detector device as an integral part of the cellular/PCS system must be provided by the cellular/PCS service provider or a third party that cooperates with the full support of the cellular network/PCS service provider.
Run optimized open source software on the backup phone. Therefore, they fool the radio antenna mast like a portable jammer and dip the frequency into a small part of the interference signal. Wrong calls may prevent text messages and calls from being sent to recipients in the area: forging identities and answering questions with strange names. In the worst case, you can even block text messages. Because the radio station will send hundreds of square kilometers of status information before being called. This process is called paging. The lead author of the study said: “You can send a call to all phones in the area.” It contains an identification number that can be used by any phone to check whether it is on the device. “However, the replacement phone will answer these questions and receive them, make calls, and send text messages faster than other phones. To the transmission tower, it seems that the actual recipient has been notified. But he hasn’t learned anything. In the best case, Only calls will be lost, no calls will be made. In the worst case, even text messages may be intercepted and read due to broken encryption and lack of authentication. So far, computer scientists have only been more than 20 years ago The GSM standard was tested, but many modern smartphones were used when necessary. The researchers said that in addition, this gap threatens the communication between the machine and the future Internet of Things. New UMTS or LTE networks may also be vulnerable. Ge Elder said: “Many GSM agreements are duplicates.