1. If the other party uses a smart phone, the incoming call firewall may be turned on, and settings such as "The subscriber you dialed is power off" or "Prohibit this incoming call" will appear.
2. If the called party is blacklisted, the other party's mobile phone will not display the incoming call, but will beep.
3. If the other party is on the phone when calling the other party, there will be a rapid beep, indicating that the other party's phone is busy at this time.
Telephone is a kind of remote communication equipment that can send and receive sound. It is generally believed that the telephone was invented by American Alexander Graham Bell in 1876. The improvements and inventions of telephone in history include: toner microphone, manual switchboard, program-controlled telephone exchange, dual-tone multi-frequency dialing, voice digital sampling and so on. In recent years, new technologies include ISDN, DSL, analog mobile phone and digital mobile phone. The improvements and inventions of telephone in history include: toner microphone, manual switchboard, dial, automatic telephone exchange, program-controlled telephone exchange, dual-tone multi-frequency dialing, voice digital sampling and so on. New technologies include ISDN, DSL, analog mobile phone and digital mobile phone.