Series PS Telestrobes® High dBA (109 dB) and low current draw One unit for most telephone systems with easy dip switch selection Standard RJ11C phone jack connection (USA) or CA-11 jack (Canada) Ideal for high ambient noise environments, quiet zones in hospitals, libraries and for alerting the hearing impaired ADA compliant Surface mounting with convenient plug-in installation Ringer is selectable on/off with dip switch setting. Approvals include: UL Standard 1459 Listed ADA Compliant For single line phones For indoor use PS-11A-WPW Powered by 115 VAC Includes a 115 VAC power cord Bright 70,000 candel power Flash (15 Candela) PS-15A-WPW Powered by the telephone analog ring voltage PS-33A-WPW AC or DC powered (no transformer included) Designed for low voltage connection