Kidde SL1771 120VAC Dual Mode Strobe Light For The Hearing Impaired The Kidde SL177I is a 120VAC wire in unit that provides a visual warning when part of an interconnected system. This unit can be directly connected with Kidde smoke alarms, heat alarms and carbon monoxide alarms. This unit provides a visual alert of danger for the hearing impaired, but they have no detection means and must be used in conjunction with operating smoke, heat or carbon monoxide alarms.