  For noisy self-sustained oscillators, both reliability, stability of a
response to a noisy driving, and coherence understood in the sense of constancy
of oscillation frequency belong to the main characteristics. Though the both
characteristics and techniques for controlling them received great attention of
researchers, owing to their importance for neurons, lasers, clocks, electric
generators, etc., these characteristics were previously considered separately.
In this paper, strong quantitative relation between coherence and reliability
is revealed for a limit cycle oscillator subject to a weak noisy driving and a
linear delayed feedback, a convectional control tool. Analytical findings are
verified and enriched with a numerical simulation for the Van der Pol-Duffing
oscillator.
