  We present a microelectromechanical system, in which a silicon beam is
attached to a comb-drive actuator, that is used to tune the tension in the
silicon beam, and thus its resonance frequency. By measuring the resonance
frequencies of the system, we show that the comb-drive actuator and the silicon
beam behave as two strongly coupled resonators. Interestingly, the effective
coupling rate (~ 1.5 MHz) is tunable with the comb-drive actuator (+10%) as
well as with a side-gate (-10%) placed close to the silicon beam. In contrast,
the effective spring constant of the system is insensitive to either of them
and changes only by $\pm$ 0.5%. Finally, we show that the comb-drive actuator
can be used to switch between different coupling rates with a frequency of at
least 10 kHz.
