Abstract: A wireless transmission device for communicating a plurality of audio streams to remote devices may include a plurality of inputs for receiving a plurality of digital audio streams, a combiner connected to the inputs for combining control codes and the received audio streams in a predetermined format to form a signal wherein the control codes for controlling the operation of a remote device equipped for processing the signal to extract the audio streams therefrom in accordance with the predetermined format, and a transmitter connected to the combiner to transmit the signal for reception by the remote device. The transmitter may include an infra-red light emitter for transmitting the signal as an infra-red light signal.

Abstract: A sharing device is composed of a distributor and multiple output units. The distributor has multiple input ports to connect different audio sources, such as VCD/DVD players, and has multiple output ports to correspondingly connect to the multiple output units. Each output unit is further connected with a sound output device, e.g. speakers, to broadcast audio signals. When the multiple output units are distributed at different locations, a user in any place is able to select a desired audio source by controlling the output unit and listen to music provided by the selected audio source.

Abstract: A method for processing sound effects in a notebook computer to support several sound effect modes. First, the method determines whether or not the pre-assigned sound effect mode is the stereo mode, assigns a line-out jack as a dual-channel output terminal and assigns a Mic-in jack as a sound-effect input terminal if the sound effect mode is the stereo mode. If the sound effect mode is not the stereo mode, a 4-channel or 5.1 -channel determination is made. If the sound effect mode is the 4-channel mode, the Mic-in jack is assigned as an output terminal for front sound effects, and the line-out jack is assigned an output terminal for surround sound effects. If the sound effect mode is the 5.1-channel mode, the Mic-in jack is assigned as an output terminal for woof and center sound effects, the line-out jack is assigned as an output terminal for surround sound effects, and the build-in speaker is assigned as an output for front sound effects.

Abstract: A wireless audio distribution system having a wireless transmitter, responsive to a plurality of audio input channels, for transmitting a encoded digital bitstream serially combining each of the audio input channel, the encoded digital bitstream further including control data disbursed therein, a receiver, responsive to the transmitted encoded digital bitstream, for decoding and demultiplexing the digital bitstream, a manual selector switch, connected to the receiver device for selecting one or more of the audio input channels to be reproduced, and a sound producing device for selectively reproducing the one or more selected audio channels in accordance with the control data.

Abstract: The method and apparatus are provided for several audio signal processing apparatuses to share at least one audio output device. Several audio signals sent from the audio signal processing apparatuses are received. The DC levels of the audio signals are shifted to a predetermined value. One of the adjusted audio signals is then selected for signal-transmitting to the audio output device. Afterwards, the DC level of the selected audio signal is re-adjusted to the predetermined value.

Abstract: A terminal connection device is adapted for connecting two voice coils in a speaker between a series connection and a parallel connection wherein the terminal connection device includes a jumper housing and a terminal switch detachably mount thereto. The jumper housing includes a jumper circuit defining a plurality of jumper inlets adapted for electrically connecting with electric outputs of the voice coils respectively and a plurality of jumper terminals electrically extended from the jumper inlets respectively. The terminals switch includes a terminal circuit electrically connected with the jumper terminals of the jumper circuit for selectively switching the voice coils between a series connection and a parallel connection.

Abstract: A method and apparatus for providing multiple channel audio in a computing system includes processing that begins by receiving an audio setup signal that indicates whether audio is to be outputted as stereo audio or multiple channel audio. When multiple channel audio is to be outputted, the line-in driver is disabled in the audio processing circuitry and the multiple channel driver of the audio processing circuitry is enabled. Thus, the multiple channel driver is operably coupled to the line-in audio jack. When the audio output is to be outputted as stereo audio, the multiple channel driver is disabled and the line-in driver is enable. Thus, the line-in driver is operably coupled to the line-in audio jack.

Abstract: A speaker system such as a public address system and a method of operation is provided. The system includes a controller and a speaker with a unique identifying address. The system may provide diagnostic information regarding a specific speaker to the controller. The method of operation of the system includes assigning a unique address to a speaker, providing communication between the speaker and a controller via an audio loop, providing communication between the speaker and the controller via a communication loop.

Abstract: The present invention has all the properties and capabilities of a standard direct-box, which is an audio adapter circuit in a rugged chassis. It allows high-impedance stereo headphones to be connected. It comes equipped with a switch that turns the signal to the exterior sound system on/off without interrupting sound to the headphones. The present invention also comes with a locking cover, which prevents inadvertent operation of additional switches, such as a ground lift switch or attenuation level switch. The cover also functions as a mounting structure.

Abstract: A system and method are provided for sensing a sound system. In one embodiment, a sound card or other such device is provided that includes an analog audio output system and a digital audio output system. Both the analog and digital audio output systems are coupled to a common audio output port through which either an analog or digital sound system is driven. The common audio output port provides a first line out and a second line out that may be employed to transmit the right and left channels of a stereo analog audio signal. Alternatively, one of the first and second line outs may be employed to transmit a digital audio signal, where the remaining line out is coupled to ground. Only one of the analog and digital output systems are enabled to transmit sound through the common audio output port to the respective sound system at a time. Accordingly, the present system and method are provided to determine whether an analog or digital sound system is coupled to the common audio output port.

Abstract: A method and system for communicating audio signals between an input device and an output device via a network. The output device can include loudspeakers and headphones. In some embodiments an output device, for example a center channel speaker, transmits audio signals to other output devices. In some embodiments, the output device is coupled to, or combined with, a speaker stand or speaker bracket. The network can be wireless, wired, infrared, RF, and powerline.

Abstract: The Stereonet Device is a switching device that contains two stages of a switching circuit. This device is for the user to input another source of an audio signal and a voice pick-up microphone audio signal to their stereo system. The users of this invention are mostly automobile drivers or passengers. This device will work with almost every stereo system in the market today. It may become a crucial stereo adapter and an important feature for future automobile stereo systems.

Abstract: In a DVE, digital voice enhancement, communication system, the selection decision for choosing which microphone to be active is based on a given function of the speech of a respective talker relative to his/her acoustic environment at the respective microphone. The selection decision is based on a selection technique normalizing at least one of a) different microphone sensitivities and b) different background noise levels at the respective microphones, preferably based on the ratio of how much louder a talker speaks over the background noise at his/her respective microphone.

Abstract: A storytelling system in which a base unit broaadcasts some blocks of audio data stored therein, and transmits other blocks of audio data stored therein to remote units either for remote broadcast, or cause the remote units to illuminate. Transmission to the remote units may be as radio signals, as ultrasound signals, as infrared signals, or as electrical impulses transmitted along wires. The blocks of data include identification codes to indicate which units are to broadcast the blocks of audio data or illuminate. The remote units have unique identifying features and are covered by matching dolls representing characters of the story. Each remote unit broadcasts the audio data appropriate to its own doll, or illuminates its own doll while the audio data appropriate to its own doll is being broadcast by the base unit.

Abstract: An audio signal processing apparatus including a plurality of jack units each of which has at least an audio signal contact piece and a control signal contact piece. A control circuit judges a kind of an audio appliance connected to each of the plurality of jack units based on a control signal obtained at the control signal contact piece, and when a function change-over command to select any one of the audio appliances is supplied, a function selecting circuit selects one of the jack units to which the audio appliance is connected. An audio appliance can be connected to any of the plurality of jack units.

Abstract: An audio reproducing apparatus including first and second audio signal transmission paths each applied with a plurality of audio signals. Each of the first and second audio signal transmission paths has a selector for selecting one of the plurality of audio signals supplied thereto and a level controller for controlling the level of the selected audio signal. The first and second audio signal transmission paths are connected to first and second speaker units respectively each for converting the audio signal selected by the corresponding selector and whose level is controlled by the corresponding level controller into acoustic power.

Abstract: An audio signal supplying device for supplying signals to an operating panel for a passenger provided in each of for many seats of a moving vehicle, such as an aircraft or a train, in which the necessity of providing a dedicated adapter or headphone or a device of a complex structure may be eliminated to save costs. The audio signal supplying device has plural operating units for passengers. For example, an operating unit 31 for the passenger has a demultiplexor 12 as a channel selection means for selecting a desired channel and a controller 61 for inhibiting part of channel selection executed by the demultiplexor 12 and for canceling such partial inhibition of channel selection by the demultiplexor 12 in response to a remote control signal received by a remote controlled light receiving unit 91.

Abstract: An addressable speaker system in which a plurality of selectively activated speakers are distributed throughout a predefined area and are connected to a central processing unit. The system contains multiple RF antennas that are capable of broadcasting and receiving radio frequency signals to individuals wearing radio frequency identification (RFID) badges. The system users the RF transmission to locate an intended radio frequency identification badge and selectively broadcasts an audio message to a speaker located closest to the intended recipient.

Abstract: A computer system audio circuit is connected to a sound device, a combination game/MIDI/line-in/line-out/headphone jack, and internal loudspeaker. The circuit routes audio signals to a headphone, when the headphones are plugged into the headphone connector of the combination jack. In addition, the audio circuit switches and does not route audio signal to the internal loudspeaker nor external loudspeakers when the headphones are plugged in. Furthermore, if the external loudspeakers are plugged into the line-out connector of the combination jack, the circuit provides audio to the external loudspeakers but not the internal loudspeaker.

Abstract: The present invention provides an audio system in an electronic musical instrument which can determine the characteristics of a reproduced sound automatically or simply for matching with the environment.

Abstract: A circuit connected between an audio signal receiver and an audio output unit can prevent an audio pop from being emitted by a speaker associated with the audio output unit. The circuit interrupts the output of the signal receiver when the DC voltage level of the system suddenly changes, e.g. when a different audio signal is selected or when the receiver is powered on or off. The output of the receiver is shunted through a resistor to ground until a blocking capacitor between the receiver and audio output unit can charge to the new DC voltage level.

Abstract: A multiple-microphone actuation control system using direction-sensitive microphones turns ON microphones only if a talker's speech originates from within a specified "acceptance angle" in front of the microphones. Additionally, the invention automatically identifies which microphone best "hears" the talker, and only turns ON one microphone per talker, while allowing several microphones to turn ON simultaneously for several talkers.

Abstract: A voice recording/reproducing apparatus includesan A/D converting circuit for converting an input analog voice signal into a digital signal;a digital signal processing circuit for coding the converted digital signal in a predetermined format and decoding the coded voice data;a recording medium for storing the coded voice data;a buffer memory;a D/A converter for converting the decoded digital signal stored in the recording medium into an analog voice signal;an operation unit for setting a predetermined mode; anda control circuit for performing a predetermined process for reducing noise in a reproducing operation to the voice data obtained from time a predetermined period of time before the operation unit recognizes that a recording stop operation is performed by the operation unit during a recording operation to time when the operation unit recognizes that the recording stop operation is performed whereby the noise due to a stop operation is reduced when the voice data is in said buffer memory and then transfe

Abstract: The living condition of a resident is prehended by a sensor disposed in a room. Identification information and vital information transmitted from a portable transreceiver carried by the resident are monitored. An audio signal favored by the resident is sequentially reproduced while the level is adjusted in accordance with the current living condition and physical condition of the resident.

Abstract: A stereophonic audio processing system having left and right stereophonic sound channels with respective loudspeakers therefor is presented. The system is provided with spatial expansion of the stereophonic sound so that a first pair of spaced-apart loudspeakers will acoustically appear to be spaced further apart then they actually are. The audio system is provided with provisions for connecting a second pair of loudspeakers which can be spatially located at a distance between the loudspeakers which is larger than the first pair of loudspeakers. The audio system is provided with apparatus for providing stereo sound without spatial expansion when such secondary loudspeakers are used.

Abstract: In an In-Flight Entertainment System (IFES), an audio distribution system transmits and synchronizes an audio data stream from multiple audio channels using the Adaptive Differential Pulse Code Modulation (ADPCM) technique for efficient transmission and preventing loss of synchronization. An encoder digitizes the analog audio signals, compresses the digital data, generates the synchronization parameters, including synchronization data for a selected channel, and creates a data frame to be transmitted to a number of decoders. Each decoder detects the synchronization header, extracts the compressed data patterns from the passenger selections, updates the ADPCM synchronization parameters, decompresses the compressed data patterns, and converts the digital audio data to analog audio signals to be delivered to the passenger seats.

Abstract: There is provided an audio communication system for a life safety system. The audio communication system includes an audio data line having a plurality of audio channels for transmitting audio data and a CPU for controlling the transmission of the audio data along the audio data line. An audio source module and an audio amplifier module are coupled to the audio data line. To produce an audible sound, the CPU selects a particular channel of the plurality of audio channels for transmitting the audio data and sends this selection to the audio source module. The audio source module then places one or more audio packets, corresponding to the audible sound, on the selected channel. The audio amplifier module then receives a signal from the CPU that identifies the selected channel and, thus, the audio amplifier module will know which channel to find the audio packets. The audio packets are converted and directed to speakers to produce the audible sound.

Abstract: The single package three channel audio signal amplifier has three amplifier channels which may be used independently to power three output loads or audio speakers or may be paralleled or bridged to increase power to one or two output loads. The integrated circuit is particularly useful for current computers which use audio devices that require signals to be processed by computer circuit boards that have power limitations. The signal amplifier allows switching between one, two and three channel operation. In addition the new device uses class D operation amplifiers which are coupled to the load by ratio transformers to provide increased efficiency and gain. The device has internal limiting and preamplifier control; allows volume adjustment, filter level and range selection, and mute and treble control; and provides on-device voltage regulation.

Abstract: A storytelling system in which a base unit broadcasts some blocks of audio data stored therein, and transmits other blocks of audio data stored therein to remote units for remote broadcast. Transmission to the remote units may be as radio signals, as ultrasound signals, as infrared signals, or as electrical impulses transmitted along wires. The blocks of data include identification codes to indicate which units are to broadcast them. The remote units have unique identifying features and are covered by matching dolls representing characters of the story. Each remote unit broadcasts the audio data appropriate to its own doll.

Abstract: A signal distribution and communication arrangement includes an electronic processor-based master control unit which controls the broadcast of different types of signals through speakers located in various zones. The system includes a telephone interfaced with a door speaker controller to allow communication between the telephone and a door speaker. A page may now be broadcast over selected speakers and zones selectively muted to allow private communication when the page is answered. Also included is a doorbell interface circuit that responds to a doorbell source. The doorbell source may be activated by any one of a plurality of doorbell switches. An additional aspect of the present invention includes grouping zones together so that all source selection works concurrently, and each subzone in the group retains independent volume control, bass and treble. Further, a new sub-set of zone programming allows the installer to label a zone as any alpha-numeric seven-digit name.

Abstract: A circuit system for selectively switching between main and remote loudspeakers includes a pair of input terminals for applying an input audio signal to the loudspeakers. A first selector switch contact is provided in series with the main loudspeakers. A second selector switch contact is provided in series with the remote loudspeakers. A current-dependent resistance element is provided in series with the remote loudspeakers to protect the remote loudspeakers from overdrive. The circuit system may also include a second current-dependent resistance element and a cooperating defeat switch contact as well as a resistor and associated load limiting switch contact all in series with the remote loudspeakers.

Abstract: A signal distribution and communication arrangement includes an electronic processor-based master control unit which controls the broadcast of different types of signals through speakers located in various zones. The system includes a telephone interfaced with a door speaker controller to allow communication between the telephone and a door speaker. A page may be broadcast over the speakers and subsequently muted to allow private communication when the page is answered. Also included is a doorbell interface circuit that responds to a doorbell source. The doorbell source may be activated by any one of a plurality of doorbell switches.

Abstract: In order to distribute music information from a central memory device (2) via a communications network (4) to a terminal (6), this information is organized in a digital music information object. The latter comprises a core having basic information relating to the music information object, as well as a number of additional layers having the actual music information. The core includes an encryption table, on the basis of which an encryption module (30) of the central memory device (2) and a decryption module (32) of the terminal (6) respectively encrypt and decrypt the music information object. Furthermore, an interpretation module (34) is provided in the terminal (6) for reproduction conditioning of the music information object, which interpretation module (34) accesses information for checking the authorized use of the music information object, which information is stored in an authorization device (36) and identifies the terminal or the consumer.

Abstract: A simple and effective stereophonic transmission system (1) wherein the transmitter (2) alternatively encodes successive block periods of a block signal with samples of the left-hand channel signal (L.sub.in) and the right-hand channel signal (R.sub.in). At receiver side, the left-hand and right-hand stereo signals are decoded from the encoded block signal by alternate integration and peak detection of positive and negative received pulses, the pulse widths of the received pulses corresponding to amplitudes of the transmitted samples. When detecting the pulses for one stereophonic channel, the corresponding other stereophonic channel is blocked.

Abstract: A signal distribution and communication arrangement includes a main control unit remotely located and electrically coupled to a volume control panel. The volume control panel is located near a speaker, and the main control unit sends substantially continuous audio signals or an interrupting audio signal to the volume control panel for playing via the speaker. These signals can be sent on the same conductor or separate conductors. When the interrupting audio signal is present, a voltage or current source provides a level from the main control unit to the volume control panel to indicate that a volume override circuit should be engaged. Upon engagement of the volume override circuit, the interrupting audio signal is passed through to the speaker at a prescribed signal level, regardless of the volume control setting on the volume control panel.

Abstract: A mono/stereo switching circuit wherein first, second, and third switches operate in circuit which is arranged so that (1) when the first switch is engaged, and the mono/stereo switch is engaged, the signal at a first mono input is provided to both of a pair of left and right output channels; (2) when the second switch is engaged and the mono/stereo switch is not engaged, the signal at a second mono input is provided to both of the pair of left and right output channels; and (3) when the input signal is a stereo signal at the first and second inputs, and either of the first and second switches is engaged, and the mono/stereo switch is engaged, the input signal at the first input terminal is provided at the left channel output while the input signal at the second input terminal is provided at the right channel output.

Abstract: An assistive listening device has a housing enclosing both infrared radiation and FM radio receivers and audio amplifier for receiving audio information transmitted to the hearing impaired audience in an auditorium by either infrared or radio radiation. The received radiation is converted to an amplified electrical audio signal. The signal is converted to audible sound by two earphones at the distal ends of two extendable arms. The arms are attached at their proximal ends to the housing. The arms have two configurations, a compact configuration in which the earphones are retracted to a position against the housing for storage or transport and an extended configuration in which the earphones are at a distance from the housing and spaced apart less than the distance between a user's ears. The arms may have one or more joints for folding compactly around the edge of the housing.

Abstract: An automated display demonstrates a loudspeaker in response to selections by a potential customer. The display permits accessible storage of the demonstrating loudspeakers.

Abstract: Dual microphones and a time-of-arrival processing circuit comprise a direction-sensing system which improves the false alarm immunity of an acoustic glass break detector by restricting its coverage to a well-defined zone. By comparing the arrival times of an abrupt sound at two spaced microphones, the processing circuit determines the direction of the sound. If the sound originated in the intended coverage zone, the processing circuit generates a signal which enables the glass break detector; otherwise, the detector is inhibited. When the improved glass break detector is oriented so that potential false alarm sources are outside the coverage zone, false alarm immunity is enhanced.

Abstract: A signal distribution and communication arrangement includes an electronic processor-based master control unit which controls the broadcast of different types of signals through speakers located in various zones. The system includes a telephone interfaced with a door speaker controller to allow communication between the telephone and a door speaker. A page may now be broadcast over selected speakers and zones selectively muted to allow private communication when the page is answered. Also included is a doorbell interface circuit that responds to a doorbell source. The doorbell source may be activated by any one of a plurality of doorbell switches. An additional aspect of the present invention includes grouping zones together so that all source selection works concurrently, and each subzone in the group retains independent volume control, bass and treble. Further, a new sub-set of zone programming allows the installer to label a zone as any alpha-numeric seven-digit name.

Abstract: A remote simultaneous interpretation system particularly suitable for oral communication between a doctor and patient who do not speak a common language includes a user station equipped with a first and second headsets and microphones, a remote simultaneous interpretation system also equipped with a headset and a microphone and an audio link operatively interconnecting the stations. The simultaneous interpreter station includes controls for routing incoming and outgoing signals from and to separate portions of the user station, thereby allowing the remotely located interpreter to listen to either the doctor, the patient or both and to route voiced interpreter signals to the doctor, the patient or both. The use of simultaneous interpretation reduces the language barrier between a doctor and a patient, thereby improving rapport and overcoming social and/or cultural barriers to providing medical care.

Abstract: An active noise eliminating system comprises microphones for detecting residual noise, speakers for generating noise elimination sound for interference with the residual noise, a noise generating condition sensor for generating noise condition, a controller for generating noise elimination signals inputted to the speakers and determined by the detected residual noise signals and the detected noise condition signal in accordance with a control algorithm including transfer functions between the speakers and microphones respectively. The transfer functions are updated on the basis of a test signal generated when noise sound diverges.

Abstract: An entertainment system for a vehicle having front and rear speakers includes a high quality entertainment system for playing a high quality medium to first passengers of the vehicle desiring high quality entertainment by outputting a high quality signal, and a low quality entertainment system for playing a low quality medium to second passengers of the vehicle by outputting a low quality signal, the second passengers having no preference between the high quality entertainment and low quality entertainment. In addition, the entertainment system includes a controller monitoring the high and low quality signals output from the high and low quality entertainment systems respectively, and outputting a control signal to control switching between the high and low quality entertainment systems and the front and rear speakers responsive to the high and low quality signals.

Abstract: An intelligent speaker unit is controlled by control data transmitted with the digital audio data. The intelligent speaker has a Digital Signal Processor (DSP) for processing the audio data in accordance with the control data. The control data contains an address to select the speaker unit. The DSP for the speaker unit processes audio data digitally based on parameters in the control data. The processed digital audio data is then converted to an analog signal which is amplified and applied to the speaker. The digital audio data is time division multiplexed on a TDM bus. Each time slot on the TDM bus contains audio data for one digital audio channel. The control data is placed on the TDM bus as one channel (time slot) or is distributed as control bits through all the other channels. The control data also contains channel select data. Accordingly the DSP in a selected speaker unit may in turn select its audio data from a plurality of audio channels based on the control data the DSP receives.

Abstract: A process for generating an entertainment audio signal interrupted by advertising audio signals in which pilot signals associated with the advertising audio signals cause switching between the entertainment audio signals and the advertising audio signals makes it possible to broadcast different radio programs of the desired acoustic quality in a shop by means of a carrier frequency. To this end, a high-frequency control signal is generated from advertising audio signals and pilot signals which precede or follow the advertising audio signals. The control signal and preferably the entertainment audio signal are modulated to a high-frequency carrier signal, possibly with several channels, for the separate recovery of the signals. The modulated carrier signal is transmitted, the transmitted carrier signal is demodulated and, if necessary, the signals are separated from each other. The pilot signals of the transmitted control signals are monitored for the presence of fading or flashback conditions.

Abstract: An audio mixer system using a serial editor interface is disclosed. Use of a microprocessor control circuit is disclosed to control various functions a plurality of multiple channel VTRs under the control of a mixer. Serial control signals are supplied from a video editor to a serial interface which includes a microprocessor. These control signals are decoded, and the appropriate controls of the VTRs are implemented. These controls include crossfading as well as PREVIEW/REVIEW monitoring.

Abstract: A dispatching console system (20) for handling communications transmissions includes a main processor (50) and a co-processor (52). The main processor (50) receives external console control commands which specify a desired settable (i.e., connect/disconnect) relationship between audio devices in communication with the console and issues main processor commands to the co-processor (52). The co-processor (52) controls a switching circuit (72) in an audio tower (24). The switching circuit (72) is a matrix of cross-point switches (220) which connects and disconnects selected communication devices. In addition to the main processor commands, desired settable relationships between audio devices can also be mandated by device activation input signals which are applied through the audio tower (24) to the co-processor (52).

Abstract: A signal distribution and communication arrangement controls the broadcast of different types of signals through speakers located in various zones. The system includes a telephone interfaced with a door speaker controller to allow communication between the telephone and a door speaker. A page may be broadcast over the speakers and subsequently muted to allow private communication when the page is answered. Also included is a doorbell interface circuit that responds to a doorbell source. The doorbell source may be activated by any one of a plurality of doorbell switches.

Abstract: The Radio Data System (RDS) protocol promulgated by the European Broadcasting Union provides for alternate frequencies (AF) for the same broadcast. Receivers periodically switch over to such an alternate frequency, leading to momentary crackling noises. In a radio receiver having a device for temporary switchover from a received frequency to some other frequency, substitute signals are inserted into the audio signals that are interrupted during the temporary switchover. The substitute signals are formed from the audio signals before and optionally also after the temporary switchover.

Abstract: A two channel audio switcher includes two analog switches, which may be implemented as a CMOS integrated circuit, receiving at their control input ports a complementary pair of drive signals, typically square wave, so as to toggle their outputs at a supersonic rate, which may be made variable. The switcher may receive as input two channels of a stereophonic source, two independent audio sources or a common monophonic source. The outputs typically drive an audio output unit such as the transmitter of a radio broadcasting system, an audio recording system, or amplifiers, controls and loudspeakers of a sound reinforcement system in an auditorium or studio. The system may be monophonic or stereophonic. In a stereophonic a.m. broadcasting system such as the Kahn independent sideband system, alternate switching allows each sideband to be modulated to full available power, thus allowing an increase in the apparent radiated power.