- The binary-input binary-output (BIBO) channel with feedback is considered, where the input sequence contains no consecutive ones, i.e., satisfies the (1, ∞)-runlength limited (RLL) constraint. For this setting, explicit expressions for feedback capacity and optimal input distribution are derived. Byproducts of this derivation are the feedback capacity and the optimal input distribution for the binary symmetric, the Z and the S channels. The solution is obtained by using an equivalent dynamic program formulation and then solving the corresponding Bellman equation. The feedback capacity also serves as an upper bound on the capacity of the input-constrained BIBO channel without feedback, a problem that is still open.