PURPOSE: To provide an MSK modem that can change its speed with which data at different transmission speed can be transmitted or received with one modem. ;CONSTITUTION: A switching circuit 3 switches the polarity of transmitting data according to a switching instruction. An MSK generating circuit 4 converts the output of a polarity switching circuit 4 based on the output of a variable frequency divider 10 to an MSK signal in a voice band and outputs it. At the time of 1200bps, the outputted MSK signal is outputted through a changeover switch for transmission as it is but at the time of 2400bps, on the other hand, it is outputted to a double balance mixer 7 for transmission. The double balance mixer 7 for transmission converts the frequency of the MSK signal and outputs that signal to a low-pass filter 8 for transmission. The low-pass filter 8 for transmission removes unwanted components and outputs that signal through a changeover switch 5 for transmission.;COPYRIGHT: (C)1995,JPO
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