Given a binary data stream

and a filter

whose output at time

is

for some complex

, there are at most

distinct values of

. These values are the sums of the subsets of

. It is shown that all

sums are distinct unless

is a unit in the ring of algebraic integers that satisfies a polynomial equation with coefficients restricted to +1, -1, and 0. Thus the size of the state space

is

if

is transcendental, if

is rational, and if

is irrational algebraic but not a unit of the type mentioned. For the exceptional values of

, it appears that the size of the state space

grows only as a polynomial in

if

, but as an exponential

with

if

.