Brent Hilpert wrote:
...
  Here's the schematic for amusement (note
measurements), pretty simple except
 for the specced coils:
   
http://www3.telus.net/~bhilpert/tmp/LDSModelAModem.gif 
The power supply has a multi stage filter to get rid of ripple.   I
would have thought investing in the extra diodes to make a bridge
instead of the half wave rectifiers would have been cheaper than the
extra C's & R's.