Some telephones, depending on the brand and model, have the intercom function, which allows to begin communication by sending the signal. When the signal comes, the telephone set rings a signal different from the standard ring tone call. After that the telephone temporarily switches off from the telephone line and works as an intercom.
Peneo is a leading-edge technology firm specializing in VoIP (Voice over IP) solutions to lower telecom costs for residential consumers (B2C), commercial businesses (B2B), and callshops/Internet cafes.