... -testing anytime;2, Alarm memory & query record function;3, LCD display concentration (3 digitals);4.Three LEDS to indicate different status ... (yellow);5, Circuit and sensor fault signal warning (alarm,LCD display & LED indication); 6.Test/Hush/Reset Button with 3 LEDS ... 7. Low Battery alarm (alarm,LCD display $ LED indication)8, Can not be fitted with bateery missingCO ...