Anti-sidetone circuit of intercom system isolation transformer

Abstract

The invention discloses an anti-sidetone circuit of an intercom system isolation transformer. The anti-sidetone circuit is characterized by comprising a first level microphone signal amplification circuit, an audio transformer, a subtractor, a direct current bias circuit and a second level noise compression amplification circuit, wherein a microphone input signal is transmitted to the audio transformer through the first level microphone signal amplification circuit; input signals of the subtractor are obtained from two different sampling points V1 and V2 in the first level microphone signal amplification circuit, and the signals of the two different sampling points V1 and V2 are respectively transmitted to an inverting terminal and a noninverting terminal of the subtractor, after the signals are processed by the subtractor, then the signals are transmitted to the second level noise compression amplification circuit, and attenuation eliminating treatment is performed on a local sidetone signal. By adopting such design, a driver transformer of an analog audio intercom system can be improved optimally, sidetones can be eliminated under full-duplex intercom, and multiple devices can be cascaded and independent mutually.

Description

technical field [0001] The invention relates to the technical field of electronic circuits for processing audio signals, in particular to a four-wire-to-two-wire drive isolation transformer sidetone elimination circuit for an intercom system. Background technique [0002] In the car intercom system, the audio intercom four-wire to two-wire solution that drives the isolation transformer not only simplifies the wiring of the car body but also enhances the anti-interference ability of the audio intercom system, which has certain practical significance in the car intercom system. [0003] In an intercom system where analog audio sending and receiving signals share one channel, in order to reduce the influence of sidetone on the call effect, all intercom equipment needs to add a sidetone canceling circuit. On the one hand, the sidetone canceling circuit makes the audio transmission signal proportional to Appearing on the transmission line, on the other hand, the signal obtained b...

AI Technical Summary

Problems solved by technology

At present, the common phase cancellation method has various circuit forms, and it can be found that these circuits are mixed with good and bad, and errors often occur, and the current car analog audio intercom system cannot solve the problem of driving transformers to achieve phase cancellation to eliminate side tone.

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