Viking Electronics 40TB IP VoIP Ceiling Speaker with Talkback MIDI Scope Ring Specification 30Mm Strobe Scope Ring Specification 30Mm 1" Aluminum Tantalum Dome Tweeter gypsum board ceiling Heavy duty back box protects speaker and circuitry against plenum dust Automatic Gain Control (AGC) to automatically increase ring volume to compensate for ambient noise Diagnostics (for testing mic red or amber strobe light (see DOD 242) Blue call status LED indicator SIP compliant (see product manual for list of compatible IP PBX phone systems) Automatic Noise Canceling (ANC) feature for operation in noisy environments Viking’s proprietary VOX switching eliminates the need for “Push to Talk” mode Selectable auto answer feature for monitoring Autoprovisioning via Viking programming software Built in high efficiency 6 watt class D amplifier Relay for activating door locks