... Button, 2xLow Level Voltage, 2xHigh Level, ACC, Engine, Door Open, Brake , 2x A/D (10bit digital,5V,12V,24V, ... Low battery voltage alarm, emergency brake, etc.Backup Battery internal, 12v, 500mAhBackup Time40minutes~90minutesSerial PortRS232Two ports, external intelligent devices such ... /temperature sensor, fix bar, and RS232 connected device Intelligent GPS car alarm system/gps tracking device/ car gps ...