To meet local code and application requirements,System Sensor offers standard 4" and 6" bases, as well as, specialty base designs including relay, isolator, sounder and low frequency sounder options for Select Series detectors. The standard 4" and 6" bases offer a plug-in detector base intended for use in intelligent systems, with screw terminals provided for power (+ and -), and remote annunciator connections. Communication takes place over the power (+ and -) lines. The 4" base offers a compact design while the 6" base provides compatibility with a wider range of junction boxes.The Select Series specialty bases support application driven requirements. The bases employ a separate mounting plate that installs on various junction box sizes to eliminate unsightly surface-mount boxes. The mounting plate enables pre-wiring of all connections to speed and simplify installation.Relay bases (B224RB-WH/B224RB-IV) provide one form C contact relay for control of auxiliary functions, such as door closure and elevator recall. The relay can operate in two different modes (short and long delay). The activation time for the short delay is 60 ms to 100 ms, while the activation time for the long delay is 6 sec to 10 sec. A shunt with pin headers, located on the base PC board, is used to set the delay timing.Isolator bases (B224BI-WH/B224BI-IV) allow the Signaling Line Circuit (SLC) loop to operate under fault conditions created from a short circuit preventing an entire communication loop from being disabled. The base isolates the section of the loop containing the short circuit from the remainder of the circuit and automatically restores when the fault is corrected.