Abstract: An existing voice band data and voice communication source, such as a residential alarm panel or point-of-sale credit/debit card reader, that includes a user phone for voice communication and which is connected through a telephone line and telephone central office to a remote receiving center through the telephone system, is provided with a communication interface coupled to said source that comprises means for enabling communication to occur over the Internet concurrently with the use of the telephone network. The system includes default circuitry which directs data communication from the source to the remote receiving center through the Internet while the Internet link is operative, and which, in the condition of a failure of the Internet link, connects both data and voice signals from the communication source for transmission of signals through the telephone network.