Abstract: A computer integrated telephone system that uses the computer's display, internal audio system, or an external interface to indicate that a voice message is waiting. The invention operates with a telephony protocol that supports in-band signaling having Message Waiting ON and Message Waiting OFF messages. The invention is embodied in a PC and includes a telephone interface that interacts with the telephone network to receive Message Waiting ON and Message Waiting OFF messages. In response to the Message Waiting ON message, the telephone interface communicates with software logic on the computer to cause the computer to indicate in an overt manner that a voice message is waiting. In response to the Message Waiting OFF message, the telephone interface communicates with software logic on the computer to cause the computer to turn off the message waiting indicator.

Abstract: A computer integrated telephony system embodied in a PC that includes a telephony interface connected to the local loop that detects whether one or more extension phones are off-hook by using the signal generating and detection capabilities found on a typical telephony interface card. In the preferred embodiment, the telephony interface is based on a programmable DSP that generates and injects onto the local loop a subsonic signal having a known shape and amplitude. If one or more extensions are off-hook, the amplitude of the subsonic signal detected on the line will be significantly attenuated. The amplitude of the detected signal is compared against a threshold value and an indication is made if the detected signal amplitude is below the threshold value.