| 摘要 |
<p>A cordless communications system includes a base unit, a cordless remote unit, and a headset. The base unit facilitates communication with alternative systems such as computer and telephone audio systems dependent upon the position of an input selection switch. The base and remote units convert analog audio signals into modulated signals that are transmitted using Pulse Position Modulated (PPM) signals. Full duplex communication between the base unit and the remote unit as well as stereo communication from the base unit to the remote unit are provided. The base unit includes a stereo pulse width modulator, a signal driver, and a pulse stream decoder. The base unit receives a PPM signal from the remote unit and recovers an audio signal produced by the cordless headset microphone. The stereo pulse width modulator produces a composite PWM signal from left and right audio signals and the signal driver uses the composite PWM signal and a clock based sync pulse stream to produce a hybrid PPM signal for transmission to the remote unit. The remote unit includes a pulse stream decoder and a signal driver. The pulse stream decoder receives the hybrid PPM signal and uses it to reproduce the left and right audio signals. The pulse stream decoder also detects the sync pulse stream within the hybrid PPM signal. The signal driver produces a remote PPM signal using the sync pulse stream and an audio signal from the headset microphone. The base unit and remote unit use a pulse modulation scheme that uses a clock and corresponding sync pulse stream to co-ordinate the timing of pulses corresponding to the left, right and remote audio signals and thus, provide full duplex audio communication.</p> |
