Abstract: Power amplifier mode control and an associated switching arrangement permit a wireless communications device, such as a mobile terminal, to advantageously use the same transmitter power amplifier in both digital and analog operating modes. Analog mode requires the mobile terminal to operate its receiver and transmitter in full-duplex mode, thus requiring a duplexer for separating the receive signal from the transmit signal. Digital mode requires the mobile terminal to operate its receiver and transmitter in half-duplex mode, eliminating the need for the duplexer. In a basic implementation, the mobile terminal includes a switching arrangement allowing the duplexer to be switched in and out of the power amplifier transmit path. For reasons of signal requirements and operating efficiency, the mobile terminal adjusts the operating point of the power amplifier such that it operates linearly or quasi-linearly when in the mobile terminal is in digital mode.

Abstract: An upstream ingress filter (300) for isolating upstream ingress noise on a bi-directional cable system having an upstream band and a downstream band for carrying upstream signals and downstream signals, respectively. The upstream ingress filter (300) includes a DC switching element (310) for changing the DC voltage on the cable system at said cable access unit and a switchable notch filter (340) that switches ON and OFF in response to the DC switching element. The notch filter isolates upstream ingress noise by attenuating upstream signals in the upstream band when the upstream ingress filter is ON. Both the DC switching element (310) and the notch filter (340) are connected in parallel to the cable (301).

Abstract: An upstream ingress filter (300) for isolating upstream ingress noise on a bi-directional cable system having an upstream band and a downstream band for carrying upstream signals and downstream signals, respectively. The upstream ingress filter (300) includes a DC switching element (310) for changing the DC voltage on the cable system at said cable access unit and a switchable notch filter (340) that switches ON and OFF in response to the DC switching element. The notch filter isolates upstream ingress noise by attenuating upstream signals in the upstream band when the upstream ingress filter is ON. Both the DC switching element (310) and the notch filter (340) are connected in parallel to the cable (301).

Abstract: A microprocessor controlled automotive audio system with radio, cassette tape, and/or compact disk media has a rear seat control with headphones allowing rear passengers to turn off the rear speakers, turn on the headphones and select any media, while the front speakers play programs selected by a front control. Rear control of media programming is also permitted if the selected media is not under front control. Rear control signals the desired function to the microprocessor which executes the commands subject to front control dominance. An audio processor couples the front-selected program to front and rear outputs and to front speakers. An audio multiplexer connects any media as well as the rear output to the rear control where a speaker/headphone switch connects the multiplexer to the rear speaker or the headphone.