CPT Piezo Buzzer Transducers CUI Devices CPT Piezo Buzzer Transducers are externally driven indicators that are available in surface-mount or through-hole mounting styles. These devices operate at frequencies up to 4.1MHz. CUI Devices piezo transducers offer a 78dB to 108dB sound pressure level (SPL) range and an operating temperature range from -40°C to +120°C. The CPT buzzer transducers are ideal for a variety of consumer electronics, industrial, and portable equipment applications.