New Automatic Noise Cancelling (ANC) feature for proper operation in noisy environments Vandal Resistant Features: 14 gauge louvered 316 stainless steel faceplate with permanent laser etched graphics, speaker/mic screen, heavy duty metal Call button and T-10 Torx security mounting screws and drive bit Weather Resistant Features: Marine grade 316 stainless steel faceplate, screws and push button switch. Switch internally sealed per IP67. Mylar speaker. Self-draining mic mount. Faceplate, mic and speaker gaskets. Telephone line powered Non-volatile E2 memory (no batteries required) Programmable to dial up to 5 numbers on busy / ring no answer Blue off-hook LED indicator Volume adjustments for microphone and speaker Advanced call progress detection: disconnects on busy signal, return to dial tone, CPC, reorder tone, maximum call time out and programmable silence time out Selectable auto-answer feature for monitoring Extended temperature range (-15 F to 130 F)