A system (130) for providing enhancement to a voice-band signal in a telecommunications network (138) is provided. The present system (130) includes a power averager (18) for determining the average power of the voice-band signal. The present system (130) also includes an equalizer (132) for attenuating a predetermined portion of the voice-band signal and an output scaler (134) for scaling the equalized voice-band signal with a scaling factor. The system (130) of the present invention also includes an automatic gain enhancer (136) for applying an automatic gain factor to the scaled voice-band signal and wherein the automatic gain factor is dependent upon the average power of the input voice-band signal.

Voice enhancement system and method

A dual resonance antenna apparatus includes an antenna element (22) and an LC parallel resonance circuit (31) for resonating the antenna element (22) in a plurality of frequency bands. The LC parallel resonance circuit (31) has a T-shaped circuit or a π-shaped circuit consisting of an inductance element (26) which is a shunt element for preventing the impedance from becoming infinitely great in a predetermined frequency band and capacitance elements (29, 30). This can eliminate a drop-in point in the frequency characteristic, i.e., notch causing deterioration of a gain.

Dual resonance antenna apparatus

This invention relates to an arrangement (14) for protecting a transducer (2) which converts an electric signal into an acoustic or a mechanic signal against overload and destruction. The arrangement is connected to the electric terminals of the transducer and changes the electric input signal under overload condition. This protection arrangement comprises a controller (15), a monitor (16) and an envelope detector (17). The monitor (16) provides a signal indicating the electric or mechanic load of the transducer (2). The peak value of the signal is anticipated by using a predictive filter in the envelope detector (17) or a delay element in the controller (15). If the predicted peak value exceeds an defined limit an attenuation element in the controller (15) is activated and the input signal is changed in time to prevent an overload of the transducer. This invention provides protection of the loudspeaker with a minimum of signal distortion and allows to reduce the head room of the transducer and to convert signals with a higher amplitude.

Predictive protection arrangement for electroacoustic transducer

Broadcast apparatus for controlling the loudness level of program signals includes a variable gain device (14) for increasing or decreasing the level of incoming program material as a function of program loudness (using control 22) while simultaneously holding (by level control 24) the output level below a preset level to assure proper modulation levels and/or to prevent excessive reaction by peak limiters (not shown) which usually follow the loudness controller in the broadcast chain.

Automatic loudness controller

An apparatus and a method modulate a carrier signal so that the resultant modulated signal varies between a value substantially equal to the quiescent level of the carrier signal and peak values up to several hundred percent of the quiescent level of the carrier signal. The apparatus includes an electrical circuit for adjusting the modulating signal so that it is clamped at a reference value to prevent overmodulation. The clamped signal controls a variable resistance mechanism which forms a part of the gain determining portion of a modulator circuit including an amplifier. The amplifier modulates the carrier signal in accordance with the gain determined by the variable resistance. The variable resistance is controlled by the clamped signal so that it causes the gain of the amplifier circuit to vary between approximately one and a value greater than one. So that the apparatus can be used by a person having a hearing impediment wherein the dynamic range detectable by the user is less than the dynamic range detectable by a normal ear, the apparatus also includes a circuit which compresses a detected acoustical signal which is within a first dynamic range into an electrical modulating signal within a dynamic range which is smaller than the first dynamic range and which is within the dynamic range perceivable by the user of the apparatus.

Amplitude modulation apparatus and method

An amplitude modulation circuit for a transmitter has an automatic level controlled circuit (ALC circuit), including in its negative feedback loop a series circuit of a high-pass filter, a rectifier circuit and an eliminator circuit, for modulation degree suppression, thereby avoiding overmodulation. The high-pass filter is so designed that the negative feedback signal level for modulation degree suppression of the ALC circuit is raised as the audio-signal frequency supplied to the transmitter increases. In the modulation circuit having such ALC circuit, a sufficiently high mean modulation degree may be obtained without encountering overmodulation if the main spectrum components of the input audio-frequency signal are distributed in the intermediate range of the audio-signal frequency band. On the other hand, if the main spectrum components of the audio-frequency signal are distributed in the higher (high-pass) range, the upper limit of the modulation degree is restricted to a moderately lower value so as to reduce production of spurious signals. Here the ALC circuit operates so as not to change the frequency characteristic of the audio-frequency input signal but to suppress the modulation degree uniformly throughout the frequency band of the audio-frequency input signal. Therefore, the modulation circuit does not cause variation in a tone quality of the input signal.

Keiichiro Kariatsumari

Papers

Amplitude modulation circuit for a transmitter