Patent ID: 6934398

Claim:
An audio switching device enabling a plurality of first audio signal processing devices to share at least one audio signal output device, the audio switching device comprising: a plurality of first pre-processing devices connecting to the plurality of first audio signal processing devices, wherein each of the first pre-processing devices receives a first audio signal from the connected first audio signal processing device and adjusts the DC level of the first audio signal to a first predetermined value; a first multitasking switch, which receives the first audio signals from the first pre-processing devices and selects one of the first audio signals for output; and a first post-processing device, which receives the selected first audio signal and adjusts the DC level of the selected first audio to the first predetermined value; wherein each of the first pre-processing devices contains a first DC level filter circuit to filter out the DC level of the first audio signal, and a first DC level adjusting circuit to receive the DC level filtered first audio signal from the first DC level filter circuit and to adjust the DC level of the first audio signal to the first predetermined value; and the first post-processing device contains a second DC level adjusting circuit to receive the selected first audio signal from the first multitasking switch and adjusts the DC level of the selected first audio signal to the first predetermined value, and a second DC level filter circuit to receive the DC level adjusted first audio from the second DC level adjusting circuit and to filter out the DC level of the first audio signal for output to the audio signal output device; and wherein the first DC level adjusting circuit contains a first resistor and a second resistor, a first end of the first resistor in electrical communications with a high level, a second end of the first resistor in electrical communications with a first end of the second resistor, and a second end of the second resistor in electrical communications with a low level; and the second DC level adjusting circuit contains a third resistor and a fourth resistor, a first end of the third resistor in electrical communications with the high level, a second end of the third resistor in electrical communications with a first end of the fourth resistor, and a second end of the fourth resistor in electrical communications with the low level.