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.
we are selling GOIP devices in Pakistan at very Attractive Price.Availability from 1 Port to 16 ports and SMB32.
contact us on email: info.brands@yahoo.com