Abstract: The conventional speakerphone using the voice switch, when combined with the echo canceler, involves a problem that the threshold for switching the transmit/receive state of the voice switch cannot comply smoothly and stably with the performance variation of the echo canceler, thereby obstructing echo canceling in a manner that the voice switch cooperates with the echo canceler. The speakerphone of the invention estimates the performance variation of the adaptive filter by using the integrated value of a power of the receive signal or the transmit signal referred in the past when the adaptive filter learns, and varies the threshold in accordance with the performance variation. Thus, the speakerphone of the invention achieves a stable communication system that approaches to the fill duplex with the voice switching system and the echo canceling system combined.

Abstract: A method is provided for communicating on an equipment network. According to the method, a message is sent from a sending equipment unit to a receiving equipment unit as a signal having a nominal power. Whenever the signal is amplified by an intermediate equipment unit through which the signal passes, the message is modified to indicate that the signal has been amplified by the intermediate equipment unit. Also provided is a first equipment unit for connection to an equipment network.

Abstract: According to a first aspect of the invention, in an echo canceler having an adaptive filter, the tap coefficients of the adaptive filter are partitioned into at least two segments, and different step gains are assigned to different segments. The step gains are used in adjusting the tap coefficients, and determine the sensitivity of the adjustment to noise in the residual signal left after echo cancellation. Comparatively small step gains are assigned to noise-sensitive segments. According to a second aspect of the invention, the step gain is switched according to the level of local background noise.

Abstract: A radio terminal is disclosed which can be switched into a talking mode simply when a telephone call terminates while sound data of music or the like is being played back and besides can assure a good talking quality. A stereo headphone microphone unit connected to a portable telephone set body includes first and second earphones and a microphone disposed in the proximity of the second earphone. Except during telephone conversation, music played back by a music playback section is enjoyed using the earphones. If a termination detection section detects termination of a call, then if music is being played back, then the playback is stopped temporarily, and a first control section supplies a ringing tone only to the first earphone and enables telephone conversation by means of the first earphone and the microphone. When the telephone conversation comes to an end, playback of the music playback section is started from a portion of the music at which the playback was temporarily stopped.