The System Sensor 2WTA-B is a 2-wire, photoelectric i3 smoke detector with thermal sensor and built-in sounder. System Sensor i3 series smoke detectors represent significant advancement in conventional detection. The i3 family is founded on three principles: installation ease, intelligence, and instant inspection. The i3 line redefines installation ease with its plug-in design. This allows an installer to pre-wire bases (included with heads). The large wire entry port and in-line terminals provide ample room for neatly routing the wiring inside the base. The base accommodates a variety of back box mounting methods as well as direct mounting with drywall anchors. To complete the installation, i3 heads plug into the base with a simple Stop-Drop 'N Lock action. i3 detectors offer a number of intelligent features to simplify testing and maintenance. Drift compensation and smoothing algorithms are standard with the i3 line to minimize nuisance alarms. 2-wire i3 detectors can generate a remote LED indicated maintenance signal when connected to the 2W-MOD2 loop test/maintenance module or a panel equipped with the i3 protocol. The SENS-RDR, a wireless device, displays the sensitivity of i3 detectors in terms of percent-per-foot obscuration. The i3 series provides wide-angle red and green LED indicators for instant inspection of the detector's condition: normal standby, out-of-sensitivity, alarm, or freeze trouble. When connected to the 2W-MOD2 loop test/maintenance module or a panel with the i3 protocol, the EZ Walk loop test feature is available on 2-wire i3 detectors. This feature verifies the initiating loop wiring by providing LED status indication at each detector.