Audio Intercom System being used in high-rise buildings or commercial complexes, provide two way communication from entrances, gates, go-downs, industrial plant rooms and normal doors, to an internal audio handset. It can be used to screen authorized visitors from outside entrance and useful to communicate internally between persons from one room to another room or office spaces. It can also be used to function as effective public announcement system.
CMOS Battery gives 'backup power' to CMOS (Complementary Metal Oxide Semiconductor) of a computer to keep some parameter values, eg: RTC (Real Time Clock). These primary parameters shall be used when the system gets booted again. Many computers use CMOS memory to hold current time and date. The CMOS memory and the clock circuit that increments the time in it are powered by a small battery called RTC, so the time is correctly updated even when the computer is unplugged.