An oscillator includes an oscillation circuit, an operation state signal generation circuit that generates an operation state signal based on an operation state of the oscillation circuit, and a first integrated circuit, the oscillation circuit and the operation state signal generation circuit are disposed outside the first integrated circuit, and the first integrated circuit includes a first digital interface circuit, a D/A conversion circuit that converts a digital signal input via the first digital interface circuit into an analog signal to generate a frequency control signal that controls a frequency of the oscillation circuit, and a terminal to which the operation state signal is input.