Intercom system: security device

An intercom also known as a talkback or a door phone is a device designed to mediate communication in private and small radius. Intercoms are electronic systems that can be farther connected to walkie talkies, mobile phones etc.

There are various types of intercoms that are used widely around the world that serve various purposes like the permanent intercom, which are basically of analogue electronics but nowadays are updated with interesting interfaces. These are generally used in schools, offices etc, however trains, air and watercrafts are utilizing this system as well.

Portable intercoms are a mixed bunch of permanent and portable stations. Venues like theatres, concert halls, auditoriums and even some outdoor sport venues like car racing use these systems stationed at the critical points. 

Some of the most commonly used intercom systems are the wired intercom systems that includes the two wired, four wired systems, the wireless intercoms, and the telephone intercoms. 

While there are varied product lines the mode of action of these utilize the same analogue components, that includes a pair of conductors of direct current of power rail ranging from 12 to 48 and a voice signal of 1 or 2 volts in average, carried from the top of these conductors. The signal transmission is carried out by using a few more conductors that conducts the voice sent in a frequency higher or lower to that of the speech frequency

Thus multiple stations can be connected simultaneously via a cable by frequency or time division multiplexing in the same domain. The wireless intercom systems however have an edge over the conventional ones. These are the easy installation ability and the choice to shift the units at anytime and anywhere,

The USA and Canada have developed more wireless products based on the same working principle, like the 49 MHz, FM band (200KH to 270 kHz), 900 MHz, 494-608 MHz, 2.4 GHz, MURS (150 MHz) and 5.8 GHz. 

A single device that can act as a means to converse or page text is what is known as the telephone intercom. This has the easiest installation and different models with different makes can be connected in an intercom system. 

However these cannot be confused with the door entry systems and these days are in extensive use around the globe in homes, schools and other venues for efficient and quick conversation and dialogues. Intercoms have now become a part of our daily lives.