Message Waiting LampProvide visual lamp indication of Message waiting and Ringing.The message waiting lamp retrofit kit is compatible with any telephone system with standard DC message waiting voltages ranging from 90VDC to 120 VDC. The LM-1A is fully modular for quick plug in installation by non-telephone personnel. The units LED will blink at stead rate when the message waiting voltage is detected. Features Include: Attractive styling,Easy retrofit mounting,Works with nearly all message waiting voltages.