Abstract: A system is disclosed which permits the user interface of a PC to be extended to the location of a remote television (TV) receiver such that video and audio signals generated by the PC may be viewed and heard on the remote TV receiver, and users at the TV receiver may control the operations of the PC through input devices located at the TV receiver. Through the disclosed interface extension system, video signals and accompanying audio signals, if any, generated by the PC are transmitted locally to a receiver coupled to the remote TV receiver. In a further embodiment, the interface extension system is used to provide multiple simultaneous interactive sessions to more than one user under the independent control of individual users located at each of several video displays, e.g. TV receivers. In that embodiment, data received from input devices located at each video display is tagged to identify the session on the PC which is controlled thereby.

Abstract: A call progress detection circuit filters the audio input along parallel bandpass and band reject paths. The relevant band of frequencies is defined by the range of 350-620 Hz, within which band all of the call progress tones are found. The energy output from the bandpass path is compared to the energy output from the band reject path to determine if the audio input is generated by a call progress tone or by vocal input.

Abstract: An input filter for coupling television signals from a signal source such as an antenna to an RF signal processing stage includes series resonant input and output sections shunting the signal path. The input section forms a trap at the video IF frequency. The output section resonates at a frequency other than the sound IF frequency, below the band of television signal frequencies to be processed by the RF signal processing stage. The filter serves to attenuate unwanted stray signals such as video and sound IF components otherwise capable of interfering with and distorting the input television signals.

Abstract: In an infrared (IR) remote control transmitter, a main amplitude regulator is provided to regulate the amplitude of pulses applied to the transmitter's driver so as to maintain infrared radiation at a level consistent with proper operation but well below a safe limit for IR radiation under normal operating conditions. An auxiliary amplitude regulator is also provided to regulate the amplitude of pulses applied to the driver so as to maintain infrared radiation below the safe limit if the amplitude exceeds a predetermined threshold level due to a component failure of the main amplitude regulator. An average detector is also coupled to the auxiliary amplitude regulator so that the amplitude of the pulses applied to the driver is reduced should their width exceed beyond a desired value due to a component failure or misoperation of the transmitter.

Abstract: An infrared remote control transmitter includes at least one infrared light-emitting diode poled with respect to a point of reference potential so as to be conductive in response to voltages having the opposite polarity of a DC supply voltage and to be nonconductive in response to voltages having the same polarity as the DC supply voltage. A push-pull amplifier is responsive to a pulse signal encoded to represent a remote control message to selectively couple the DC supply voltage or the reference potential to a capacitor coupled in series between the push-pull amplifier and the light-emitting diode. The capacitor is charged and discharged and an alternating drive voltage for the light-emitting diode having portions with polarities both the same as and opposite to the polarity of the DC supply voltage is generated.