Abstract: An improved speakerphone that may be viewed as a modification of a conventional half-duplex speakerphone that includes transmit and receive attenuators for alternatively isolating either a speaker or a microphone from a phone line. The attenuators are controlled by a controller that compares a signal generated by the microphone with a signal received on the phone line to determine which of the transmit or receive attenuators should be turned on. In the present invention, a first variable gain amplifier is connected so as to amplify the signal generated by the microphone prior to the signal being connected to the controller, and a second variable gain amplifier is connected so as to amplify the signal received on the phone line prior to the signal being connected to the controller.

Abstract: A method and apparatus for connecting remote options to a digital telephone base. Physical and communications protocols for connections and a flexible control scheme which can be as simple or elaborate as a given option requires are provided. The digital telephone includes an option bay connection, having a hierarchical control protocol. The option bay connection makes available several types of information, including: local analog audio, analog voice, digital voice, digital data and telephone control streams.