In this paper we consider finite-dimensional generalized linear
discrete-time-invariant systems in the form Ex˙ (k+1) = Ax(k)+Bu(k), y(k) =
Cx(k) where E,A 2 M = Mn(C), B 2 Mn×m(C), C 2 Mp×n(C), describ-
ing convolutional codes. The notion of output observability is analyzed and a
characterization of output observable systems is obtained.