Discrete-Time Systems. Examples Accumulator- Input-output relation can also be written in the form yn=∑x[(+∑x[( C=0 =y-1]+∑x[(ln≥0 C=0 The second form is used for a causal input sequence, in which case y-l is called the initial condition Copyright C 2001, S K MitraCopyright © 2001, S. K. Mitra 4 Discrete-Time Systems:Examples • Accumulator- Input-output relation can also be written in the form • The second form is used for a causal input sequence, in which case is called the initial condition = + = − =− n y n x x 0 1 [ ] [ ] [ ] [ 1] [ ], 0 = − + = n y x y[−1] n 0