Model SK-PHOTO-R-W is a plug-in type smoke sensor that combines a photoelectronic sensing chamber with addressable-analog communications. When used in duct applications with a DNR(W), testing can be done remotely using approved System Sensor test accessories, eliminating the need for a test coil. The sensors transmit an analog representation of smoke density over a communication line to a control panel. Rotary dial switches are provided for setting the sensor’s address.