A first oscillation circuit and a second oscillation circuit are connected to a first pressure sensor and a second pressure sensor, respectively and oscillate based ON the capacity values of the corresponding pressure sensors. The first oscillation circuit and the second oscillation circuit operate in response to instruction from a CPU. The one of the first oscillation circuit and the second oscillation circuit that has received an activation signal from the CPU outputs a signal having a frequency that corresponds to the capacity value of the corresponding pressure sensor. An adjustment circuit is connected to the first oscillation circuit and the second oscillation circuit, and allows one of the frequency signals to pass therethrough and outputting the signal to the CPU.
