                         SUBPROGRAM FR

After a series of stages are designed with the help of subprograms PZ,
RP, RPCHECK and MPP, the overall response of the cascaded sections can be
checked out using this subprogram.

   The output of the above subprograms will be the input of this subprogram.
In some cases the input data may come from other sources, for instance in
the case of a simple RC section. The data is entered by answering specific
questions for each section in turn. So it would be well to have on hand the
printouts from the above subprograms where needed. After each stage is entered
the final answer given is 'end' or 'E' and the program will compute the
response of the cascaded stages. This can then be compared with the response
predicted by PZ so as to confirm that the stages have been designed correctly.

More than one frequency response calculation can be made, focusing on different
frequency intervals if desired.

***
                         PROGRAM OUTPUT

The output is sent to disk files. For the first run the name of the file will
be FR1A for the first frequency response, FR1B for the second frequency
response etc. If new data is entered then the output files will be called
FR2A, FR2B etc. When the program is stopped completely and started
again these same names will be reused and the program automatically renames
the old files by adding a letter to the end of the file name to produce a
new unique file name.

Once out of the program and back in DOS these programs can be accessed by
commands such as these:

A:\> type b:fr1a       { to write on the screen; the screen can be }
                           { stopped and started using control-s       }
A:\> print b:fr1b      { if a printer is present }
A:\> copy b:fr2a prn   { if a printer is present }

Inside the program they can be examined using the BROWSE option of the menu.
***
                          GRAPHICS

During subprogram FR the user has the option of examining the frequency
response using the FV graphics option. If the output files are to be used for
graphics then it is advisable to use sufficient sample points to make a smooth
curve. The minimum should be 50 and the graphics can handle at the most 200.
If the output files are to be used as printed files then any number of points
may be used. If the user expects to plot with a log frequency axis then best
results will be obtained using the log option for the plotting intervals.
The graphics option may be used later so long as the output files remain in the
directory.
***
