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.
SunComm Technology Co., Ltd. Core members have been engaged in the communication & networks industry since 1977. Their main products in 2009 focus on GSM, VoIP, 3G Devices.