18KHz. Intercom: Supported, Integrated Microphone. Operating Temperature level: -20 ～ 50 ℃. SPON Communications Measurements: 283.1 * 224.3 * 269mm. Network Ceiling Speaker GEN-6211A03 Power Supply: DC 24V/1A or POE. Interaction Methods: TCP/IP, UDP, SIP, ONVIF. Signal-to-Noise Proportion: > 80dB. Frequency Action: 100Hz

In 1690 Christiaan Huygens, a Dutch scientist, postulated that a light wave progresses for the reason that each issue in it will become the centre of a little bit wavelet travelling outward in all Instructions in the velocity of light, Just about every new wave remaining just the envelope of these expanding wavelets. If the wavelets reach the area