  It has been found that noise plays a key role to improve signal transmission
in a one-way chain of bistable systems [Zhang et al., Phys. Rev. E 58, 2952
(1998)]. We here show that the signal transmission can be sharply improved
without the aid of noise, if the one-way chain with a single source node is
changed with two source nodes becoming a Y-shaped one-way chain. We further
reveal that the enhanced signal transmission in the Y-shaped one-way chain is
regulated by coupling strength, and that it is robust to noise perturbation and
input signal irregularity. We finally analyze the mechanism of the enhanced
signal transmission by the Y-shaped structure.
