Imagine two groups of spectators, each multiplying two
2-digit numbers on a pocket calculator to arrive at a
totally random 4-digit number. The performer writes a
prediction and sets it aside. He then begins to slowly
reveal the numbers that make up the 4-digit products arrived
at by the spectators. The mulitplication is then done by
longhand to show that the calculator's products were
correct. For the mind-numbing finish, the two products are
added together and found to match the performer's
prediction.

This routine, originally featured in Osterlind's Dynamic
Mysteries, has not been widely performed due to the
difficulties in obtaining the proper apparatus. Now, with
DIGITAL FEEDBACK, you'll be able to add this powerful
routine to your own show.

You receive the very special scientific calculator,
hand-modified by Richard Osterlind, plus a manuscript which
describes this powerful routine, in addition to other
possible effects. Please don't confuse this with other
calculators that have been on the market. The DIGITAL
FEEDBACK calculator is totally examinable and will function
normally, yet its secret will allow you to do very
extraordinary things!

MY COMMENTS:
Digital Feedback comes with the calculator and a thin
instruction booklet, essentially four pages long, which
details the routine. This routine is certainly a strong one
and the calculator is an extremely versatile prop that can
be used for many, many different presentations, not just
this one.  Incidentally, this routine was originally
published in Dynamic Mysteries, which is, at the time of
this writing, out of print. The routine was also featured
on Mind Mysteries Too Volume 5.

By the way, to clarify the first sentence ("Imagine two
groups of spectators, each multiplying two 2-digit numbers
on a pocket calculator to arrive at a totally random 4-digit
number"), the two groups do not work at the same time.  Only
the one calculator is involved.

Although this is an altered calculator, it is NOT a
forcing calculator (see Banachek & Gene Protas' Psi-Kalc if
you're looking for one).  This has a far more devious
function in mind.  However, the booklet also includes a
bonus routine that takes advantage of a certain sequence of
keys that will turn many scientific calculators into a
forcing calculator. This is certainly a valuable utility item
that you should seriously consider adding to your arsenal of
mentalist's tools, especially if you do demonstrations with
numbers.