Abstract: A headset telephone having an in-use indicator for notifying passers-by when the wearer of the headset is carrying on a telephone conversation. In one embodiment of the invention, an in-use indicator comprising a light-emitting diode is disposed on the end of the headset's voice boom, and is illuminated in response to activation of the headset. In another embodiment of the invention, activation of the headset causes a transmitter to transmit a signal to a remote in-use indicator not physically connected to the remainder of the telephone system.

Abstract: An improved noise cancelling apparatus is disclosed combining a unique directional noise cancelling microphone structure with a noise reducing, signal shaping electronic circuit. The microphone structure simultaneously receives two input signals; a first signal containing only ambient noise and a second signal containing both ambient noise and a voice signal. The microphone structure cancels the two noise components and transmits the voice signal into an electrical signal. The electronic circuit further processes the electrical signal to suppress any noise components not cancelled by the microphone structure. The electronic circuit also functions to enhance the high frequency components of the voice signal to provide a richer, more pleasant sounding output. Because the unique microphone structure is combined with the electronic circuit the noise cancelling apparatus of the present invention provides a cleaner, more pleasant sounding output than that of the prior art.

Abstract: A telephone headset apparatus for use with an existing cellular telephone. The headset apparatus is modularly connectable to the existing cellular telephone system, and no electrical or mechanical modification of the existing telephone system is required. A "handset primacy" feature of the headset apparatus ensures that normal handset operation of the cellular telephone system is unaffected by the installation of the headset apparatus. In addition, the handset may remain resting in its cradle even while the headset is operated. A slave unit connects with the cellular telephone's transceiver unit, and a headset control unit connects both the headset and handset to the slave unit. The headset control unit contains a pushbutton for selecting headset operation, as well as a volume control dial for controlling the volume of sound reproduced by the headset's earpiece.