2. Three-way call. This is a new service based on call waiting and holding. The three-way call function of the mobile phone can realize a total of six-way calls including speakers at most.
3. Instructions for use: After hearing the tone, press the number A, press the number # to end, and after dialing, press the number * to dial another phone.
4. Note: The mobile phone of the organizer of three-way call must be able to support this function, and call waiting/call holding needs to be turned on at the same time when using three-way call.
5. Principle: In the past, automatic exchange or program-controlled exchange used three-way communication, but in the era of mechanical contact control (a few years ago), it was still more troublesome to realize. It uses three or more carriers for training, so that the carriers are isolated from each other. Only when voice signals are compared by a comparator can they not collide, and then they are connected together through electrical connectors, thus realizing multi-channel simultaneous call. It means that it is similar to receiving several calls on our telephone line at the same time, but because the third party is remote rather than local, it needs a more complicated adjustment process.