18KHz. Intercom: Supported, Built-in Microphone. Operating Temperature level: -20 ～ 50 ℃. Measurements: 283.1 * 224.3 * 269mm. Network Ceiling Speaker GEN-6211A03 Power Supply: DC 24V/1A or POE. Communication Procedures: TCP/IP, UDP, SIP, ONVIF. Signal-to-Noise Proportion: > 80dB. Frequency Feedback: 100Hz https://fernandotnctg.blogvivi.com/30567577/picking-the-right-ip-speaker-key-features-to-take-into-consideration