Abstract: At a telephone subscriber's premises, call identification apparatus is used to determine whether incoming calls are intended for a primary telephone station or for a secondary telephone station. The call identification apparatus monitors electrical signals present on a telephone line after the call has been answered by one of the secondary telephone stations in search of a predetermined identificattion signal. In response to the presence of the identification signal from an originating source, the apparatus disconnects all secondary stations from the telephone line, terminates the incoming call by hanging up, and dials a predetermined telephone number. After dialing the predetermined number, an authentication procedure is invoked which requires that the dialed station transmit a security code to the apparatus. If the dialed station incorrectly transmits the security code more than N times, the call is terminated.