Transcrypt International, Inc.

Transcript International, Inc.

James R Holthaus

Christopher Aaron Hall

David L Dilley

Douglas E Ehlers

Bradley A Riensche

Max Aaron Caldwell

Voice security between a composite channel telephone communications link and a telephone

An apparatus and method for improved security in wire or wireless communication systems includes scrambling the audio signal, combining a masking signal with the scrambled audio signal, and then transmitting the scrambled masked signal. To recover the original audio, a receiver must by synchronized and know the characteristics of the masking signal and the scrambling technique. Such a receiver removes the masking signal, descrambles the audio and thus recovers the original audio. Any attempted interception of the communication would hear white noise, and even if the white noise mask where removed, the communication would still have the security level of the scrambling. The mask removes any remnants of the original audio that might be used to try to locate and intercept the communication.

Apparatus and method of secured analog voice communication

An apparatus and method for providing proper bias current and load resistance for a telephone microphone regardless of the type of microphone used. Microphone bias voltage, if any exists at the microphone, is compared to a reference voltage selected to define a distinction between various types of microphones. If the bias voltage exceeds the reference voltage, an impedance matching the correlated type of microphone is interdicted on both sides of the microphone. If reference voltage exceeds bias voltage, a different impedance path is presented to match it with the type of correlated microphone. Therefore, the invention automatically provides proper bias current and load resistance for the microphone.

Apparatus and method for providing proper microphone DC bias current and

An apparatus and method for determining the presence and polarity of DC bias voltage at a telephone microphone. A circuit can be added in parallel between any hand or headset and a telephone base unit. The circuit converts the DC bias voltage, if any, across the microphone into a pulsed signal. Each pulse charges a capacitor. The output of the capacitor is passed through a resistor transformer network, and sampled. In between each pulse, the capacitor is discharged and the resulting signal is passed through the transistor/resistor network and sampled. By determining the averages of the charging and discharging signals, and sampling them to convert it into digital information, a digital signal processor can derive whether any bias voltage is present across the microphone, and, if so, its polarity. The circuit can be electrically isolated from the microphone and telephone.

Apparatus and method for determining the presence and polarity of direct

An apparatus and method for voice privacy for cellular phones includes generic connection points to make it universal for most cellular phones. The connection points include the speaker and microphone and the microphone input and speaker output of the cellular phone. A scrambling or encryption circuit or process is used to secure the audio before it is transmitted over the network, and the unsecured audio once received. Side-tone added by the cellular phone and network echo of the scrambled audio to be transmitted is removed by, for example, adaptive echo cancellation, and unscrambled side-tone is presented to the speaker. The apparatus can be implemented in a digital signal processor.

Growing community of inventors

Omaha, NE, United States of America

James R Holthaus