The touch-tone telephone belongs to the third generation, and the first two generations have been gradually eliminated. It currently accounts for 90% of domestic telephone production and is also a major export product.
Digital cordless phone
The auxiliary unit communicates with the landline "radio". The user is connected to the switch through the landline, and the mobile phone can make or receive a call within a certain distance from the landline. The mobile phone can also talk to the landline, which will gradually replace the third generation wired telephone.
With the LCD display, you can avoid dialing the wrong number, which is also good for controlling the call time.
In addition to the complete fixed telephone function, it also has a large-capacity business card management function, incoming and outgoing call management function, telephone harassment prevention function, and many functions to assist the office.
Sound and electricity interchange
For fast, long-distance communication, you cannot directly transmit sound, but you must first turn the sound into an electrical signal (that is, use electricity as a carrier), and then return the electrical signal to sound after arriving at the other party.
Automatic telephones send dial signals to direct the work of telephone exchanges and establish a connection between two telephones.
When the caller picks up the phone, the switch should have the ability to know "someone wants to make a call" so that the switch is ready to connect.