When discussing mobile phone signal blocking technology, the following legal, ethical and technical restrictions must first be clarified： ### Technical level 1. **Signal interference equipment exists** A mobile phone signal blocker (Jammer) can theoretically block the connection between a mobile phone and a base station by transmitting radio waves in a specific frequency band to interfere with communication signals. But： -**Limited coverage**: Civilian equipment usually only covers a small area (such as a single room). -**Frequency band restriction**: It is necessary to cover all carrier frequency bands (2G/3G/4G/5G, Wi-Fi, etc.) before it can be completely blocked, which is technically difficult. -**Satellite communication cannot be blocked**: Some high-end mobile phones support satellite emergency distress (such as iPhone 14+/Huawei Mate 60), but ordinary blockers are invalid for this. 2. **Technical countermeasures** Modern mobile phones may automatically switch signal sources (such as enabling Wi-Fi Calling), or indirectly send distress signals via Bluetooth/Wi-Fi connection to other devices. ### Legal and ethical risks 1. **Illegality on a global scale** -**China**: According to the "Regulations of the People's Republic of China on Radio Administration", unauthorized use of signal blockers can face equipment confiscation, fines (up to 5,000 yuan) and even criminal liability. -**U.S./European Union**: The FCC and national regulatory agencies strictly prohibit civilian jamming equipment, and violators may face fines or imprisonment of tens of thousands of U.S. dollars. -**Emergency service hazards**: Interference signals may block emergency calls such as 110/120, endangering public safety. 2. **Ethical issues** The use of such technologies to prevent others from seeking help is suspected of serious crimes such as illegal detention and kidnapping, which violates basic human rights. ### Legal alternative 1. **Personal safety protection** -**Mobile phone emergency function**: Enable SOS emergency call (press the power button 5 times in a row), share real-time location (such as Apple “Find” or Google Maps sharing). -**Security APP**: Install one-click alarm applications such as ”Be Afraid“ and ”Public Security 110". 2. **Institutional/home protection** - **Signal shielding needs to be licensed**: Only prisons, military facilities and other places approved by the government can legally use shielding equipment. -**Physical isolation**: Use a room made of Faraday cage to block the signal (legal authorization is still required). 3. **Social collaboration** -The monitoring system of public places and the rapid response mechanism of the police are more effective in preventing crime than signal shielding. ### Conclusion Any attempt to restrict the freedom of communication of others by blocking signals is illegal and unethical. If you are worried about security issues such as kidnapping, you should improve your protection through legal means (such as security equipment and police cooperation), rather than adopting illegal technical means.