Programming the 73M2901CE Call Progress Monitor Filter

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 they were not originally intended to do, for instance detecting and generating tones
that are not normally used for normal modem functions.
 
Although all the 73M2901CE modem is preprogrammed for most normal dial-up low speed modem applications, in
some cases it may be desirable to detect frequencies that are not part of its default set.  The 73M2901CE modem
can be programmed to detect and generate other frequencies beside the ones normally used.  This application
note describes the procedure for modifying the detect frequency band of the imprecise call progress detector of the
73M2901CE.  Another app note covers the programming of the precise Call Progress Detectors (CPD), there are
also detectors that can be selected that cover a wider range that can also be modified so they can be used for
other detection purposes.  This application note provides some insight only into how the imprecise detector can be
programmed to detect frequencies other than those normally provided.