What type of oscillator uses a tapped coil in parallel with a capacitor?

The Hartley oscillator is a type of LC oscillator that specifically utilizes a tapped coil in parallel with a capacitor to produce oscillations. The configuration of the tapped coil allows for selective tuning, enabling the oscillator to operate at a desired frequency. In this setup, the positive feedback necessary for oscillation is achieved through the varying inductance provided by the tap on the coil, along with the capacitance in parallel. This combination is crucial for establishing the resonant frequency of the circuit, which is determined by both the capacitance and the effective inductance from the tapped coil.

The other options do not fit the description provided. The LC tank oscillator typically refers to a configuration that does not specifically use a tapped coil but relies on a combination of an inductor and a capacitor to create resonance. The crystal-controlled oscillator uses a quartz crystal to stabilize the frequency, making it distinct from the tapped coil setup of the Hartley. Monostable multivibrators, on the other hand, are not oscillators in the sense of generating continuous waveforms; instead, they produce a single output pulse in response to a trigger. Thus, the Hartley oscillator stands out as the correct answer due to its specific construction and operational mechanism involving a tapped coil and a capacitor