Patent ID: 8254560
Filing Date: 2012-08-28
Classification: H04M

Abstract:
1. An oscillation-echo preventing circuit for use in two-way communication equipment or in one-way communication apparatuses, said circuit comprising: a microphone/speaker unit including: a voltage-canceling circuit for canceling voltages of audio receive signals; a voltage-changing circuit for distributing the voltages of audio signals received from the microphones; and a control circuit for controlling the voltage-changing circuit and including: wherein the microphones are configured to detect, at the same time, the vibration of the fluid, caused by an audio receive signal in the first inside space, and the vibration of the fluid, caused by an audio transmit signal coming from the outside space, the speaker or earphone is configured to apply sound into the first inside space and the outside space at the same time, the voltage-canceling circuit is configured to cancel the voltages of the audio receive signals coming from the microphones, thereby generating an output of minimum magnitude, the sum of the voltages of the received audio signals automatically becomes minimal when the sum of the received audio signals is not fully minimal at the time of detecting the vibration of the fluid, caused by the audio receive signals in the first inside space, because the components of the voltage-canceling circuit undergo temperature change and aging in changing environment.