Complex sentence: In a tuned oscillator the period of the output may be controlled by altering the resonant frequency of the system, in the case on a tunable electronic oscillator this is most commonly achieved by altering the capacitance of the circuit.
Split into simpler sentences: In a tuned oscillator, the period of the output may be controlled by altering the resonant frequency of the system. In the case on a tunable electronic oscillator, this is most commonly achieved by altering the capacitance of the circuit.