JPS6220440A - Privacy telephone system - Google Patents

Abstract

PURPOSE:To prevent a wiretapper from finding the presence/absence of a sound signal by dividing a signal in the sound band into plural frequency regions and combining transposition and inversion and adding tone signals having the frequencies of intervals of frequency division. CONSTITUTION:The signal in the sound band is divided into plural frequency regions by band pass filters BPFs 1-3. Outputs of BPFs 1 and 3 are inverted and are transposed. Tone signals having the frequencies of intervals of frequency division are added by tone oscillators, and a synthesized signal is transmitted. In the reception side, the reception signal is divided into plural frequency regions by the same filters as the transmission side, and the transposition and inversion in the order opposite to that in the transmission side are performed, but a tone signal eliminating circuit circuit is made unnecessary.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は音声信号の秘話化の方式に関する。[Detailed description of the invention] [Industrial application field] The present invention relates to a method for polarizing audio signals.

〔従来の技術〕[Conventional technology]

従来より音声信号を秘話化する手法としては、音声信号
を複数の周波数領域に分割し、これらの入ｎ換えと領域
内で周波数反転を組合せて送信する方法が知らｎている
。Conventionally, as a method of polarizing an audio signal, a method is known in which an audio signal is divided into a plurality of frequency regions, and a combination of shuffling these frequencies and frequency inversion within the region is used for transmission.

〔発明が解決しようとする問題点〕[Problem that the invention seeks to solve]

上述した従来の秘話方式は、秘話化さａｆｃ音声を秘話
復調回路を通さないで盗聴したときには周波数軸上での
加工がさ几ているだめ原音とは全く似ていない復調音と
なる。しかし、振幅軸上での加工はなさｎていないため
、原音声の調子、ｔなわち現在しゃべっているのだ黙っ
ているのか、長い言葉を発したのか短かい言葉を発した
のかについては容易に判明してしまう。このだめ、盗聴
者に現在秘話のかかった人間の音声が送られているとい
う重要な情報を提供することになり、かえって解読への
興味をそそるという欠点がある。In the above-mentioned conventional confidential communication system, when the confidential communication AFC voice is eavesdropped without passing through the confidential communication demodulation circuit, the processing on the frequency axis has not been completed, resulting in a demodulated sound that does not resemble the original sound at all. However, since no processing has been done on the amplitude axis, it is easy to determine the tone of the original voice, whether it is currently speaking or silent, and whether it has uttered long or short words. It turns out. This method has the drawback of providing the eavesdropper with important information that the confidential human voice is currently being transmitted, which may actually arouse interest in decoding it.

Ｃ問題点を解決するための手段〕 本発明は、秘話化された信号を盗聴してもそれが人声を
秘話化したものであることを容易にはわからなくするた
めに、秘話化回路の出力信号に更にトーン信号を重畳す
る回路を有している。このため、盗聴さ几た場合にも常
にトーン信号が聞こえることになる。Means for Solving Problem C] The present invention provides a polarization circuit in order to make it difficult to tell that even if a polarized signal is intercepted, it is a polarized human voice. It has a circuit that further superimposes a tone signal on the output signal. Therefore, the tone signal will always be heard even if eavesdropping occurs.

〔実施例〕〔Example〕

第１図および第２図はそｎぞｎ本発明を実施した秘話化
器の構成および各部の周波数スペクトラムの例である。FIGS. 1 and 2 are examples of the configuration and frequency spectrum of each part of a polarizing device embodying the present invention.

本例では帯域を３分割し、その中２つについては反転を
施した後、順序を入ｎ換えている。トーン周波数は正確
に帯域分割周波数に合致している。In this example, the band is divided into three parts, two of them are inverted, and then the order is changed. The tone frequency exactly matches the band division frequency.

第３図および第４図はそｔぞれ第１図の秘話化器に対向
で使わｎる秘話復号器の構成および各部のスペクトラム
の例である。第３図に示した構成例は、本発明を実施し
ないとき、即ちトーン信号が重畳されていないときに使
われるものと全く同じである。トーン信号の除去回路を
特に設けない理由は以下の通りである。すなわち、もと
もと帯域分割を行なう秘話信号においては、フィルター
で周波数分割を行なう以上、丁度分割周波数の信号は復
調さｎない。もし、復調できるようにフィルターの帯域
が重なるようにしたりすると、隣接領域にはみ出した部
分の信号が非正規の周波数位置に復調されてしまうから
である。このため、重畳したトーンを分割用のフィルタ
一群の境界の非復調領域に選ぶことにより、除去フィル
ターを省略する事ができる。3 and 4 are examples of the configuration and spectra of each part of a polarization decoder used opposite to the polarization device of FIG. 1, respectively. The configuration example shown in FIG. 3 is exactly the same as that used when the present invention is not implemented, that is, when no tone signal is superimposed. The reason why a tone signal removal circuit is not provided is as follows. That is, in the case of a secret signal which is originally subjected to band division, since frequency division is performed by a filter, the signal at exactly the division frequency is not demodulated. This is because if the bands of the filters are made to overlap so that they can be demodulated, the portion of the signal that protrudes into the adjacent region will be demodulated at a non-normal frequency position. Therefore, by selecting the superimposed tone as a non-demodulation region at the boundary of a group of filters for division, the removal filter can be omitted.

〔発明の効果〕〔Effect of the invention〕

以上説明したよりに、本発明は秘話化回路側に簡単なト
ーン発振器を追加するだけで、伝送路上の秘話のかかっ
た信号から音声の有無を知ることを困難にする効果が得
らｎる。As explained above, the present invention has the effect of making it difficult to determine the presence or absence of voice from the confidential signal on the transmission path by simply adding a simple tone oscillator to the polarizing circuit.

なお、説明した例では帯域３分割で、その一部を周波数
反転する例を示したが、本発明の方式は帯域２分割や４
分割以上の秘話方式や、周波数反転を伴わない方式にも
容易に応用可能である。In addition, in the example explained, the band is divided into three parts and a part of it is frequency inverted, but the method of the present invention can be divided into two parts or four parts.
It can also be easily applied to a confidential communication method that involves more than division or a method that does not involve frequency inversion.

【図面の簡単な説明】[Brief explanation of drawings]

第１図および第２図はそれぞれ本発明の秘話化器の構成
例および各部の周波数スペクトルの説明図。第３図およ
び第４図はそｎぞｎ本発明の秘話復調器の構成例および
各部の周波数スペクトルの説明図。　　　　　　　　　
　　　　　　　　−〜。FIG. 1 and FIG. 2 are explanatory diagrams of a configuration example of a polarization device of the present invention and frequency spectra of each part, respectively. FIG. 3 and FIG. 4 are explanatory diagrams of an example of the configuration of the secret demodulator of the present invention and frequency spectra of each part.
-~.

Claims (1)

【特許請求の範囲】[Claims] 音声帯域の信号を複数の周波数領域に分割し、周波数軸
上で領域間の入れ換えや領域内の反転を組合せて送信し
、受信側で前記入れ換えや反転の逆操作を行なうことに
より伝送路上の信号を秘話化する方式において、送信側
にて周波数分割の切れ目となる周波数のトーン信号を付
加して送信することを特徴とする秘話方式。The signal on the transmission path is divided into multiple frequency regions, transposed between the regions on the frequency axis, and inverted within the region, and then transmitted, and the receiving side performs the reverse operation of the transposed and inverted operations. This method is characterized in that a tone signal of a frequency that is a break in frequency division is added and transmitted on the transmitting side.