First and second piezoelectric transducers 2 and 3 are fixed to a tubular main body 1 via first and second fitting bases 4 and 5. On front and rear surfaces of an end portion of each of the first and second piezoelectric transducers 2 and 3 are provided first and second electrodes 6 and 7. When the tubular main body 1 is secured to a circuit box, each of the end portions of the first and second piezoelectric transducers 2 and 3 is inserted between first and second contact members provided on the circuit box such that the first and second electrodes 6 and 7 are electrically connected to the first and second contact members, respectively to connect the first and second piezoelectric transducers 2 and 3 to the circuit box by one touch operation.