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.
Established in year 2000, C3Call Telecom Group hold licenses in Singapore, S Korea, Vietnam and Cambodia to provide telecommunications services to its partners. Today, we are interconnected to more than 100 telco partners worldwide.