精確的頻率檢測器及音頻產(chǎn)生

　　The Teridian 73M2901CE integrated circuit modem provides all the microprocessor control, modulation, and demodulation functions required to implement a V.22 bis 2400 bps modem. There are some ways to make the 73M2901CE do functions that it was not originally intended to do, for instance detecting and generating tones that are not normally used for normal modem functions.

　　Although all the 73M2901CE is preprogrammed for most normal dial-up low speed modem applications, in some cases it may be desirable to detect and/or generate frequencies that are not part of its default set. The 73M2901CE can be programmed to detect and generate other frequencies beside the ones normally used. This application notes describes the procedure for modifying the detect frequencies of the precise call progress filters of the 73M2901CE.