Useful Links & Definitions:

Private Branch Exchange. A small, privately-owned version of the phone company's larger central switching office.

Residing in an enterprise, a PBX is a piece of equipment that is responsible for switching calls between enterprise users. The PBX allows the users to share a specific number of external phone lines, saving the added cost of having an external phone line for each user.

Piece of telecommunications equipment installed in a company's office, which makes it possible to connect many internal telephone lines to city telephone lines

A Private Branch eXchange (also called PBX, Private Business eXchange or PABX for Private Automatic Branch eXchange) is a telephone exchange that serves a particular business or office, as opposed to one a common carrier or telephone company operates for many businesses or for the general public.

PBX Functions :

Functionally, the PBX performs three main duties:

Establishing connections (circuits) between the telephone sets of two users. (e.g. mapping a dialed number to a physical phone, ensuring the phone isn't already busy)

Maintaining such connections as long as the users require them. (I.e. channeling voice signals between the users)

Providing information for accounting purposes (e.g. metering calls)

In addition to these basic functions, PBXs offer many other capabilities, with different manufacturers providing different features in an effort to differentiate their products. Common capabilities include (manufacturers may have a different name for each capability):

• Intercom Call
• Automatic Call Back
• Caller ID
• Trunk Caller ID
• Call Billing (ASMDR)
• Call forwarding on absence
• Call forwarding on busy
• Call park
• Call pick-up
• Call transfer
• Call waiting
• Camp-on
• Conference call
• Brokers Call / Quick Conference
• Custom greetings
• Customised Abbreviated dialing (Speed Dialing)
• Direct Outward Dialing (DOSA)
• Direct Inward System Access (DISA) (the ability to access internal features from an outside telephone line)
• Do Not Disturb (DND)
• Follow-me
• Music on hold
• Auto Day -Night Service
• Auto Lunch Mode
• External Music Input
• Voice paging (PA system)

Telephone history :

Alexander Graham Bell (1847-1922) is most famous for his invention of the telephone. As a teenager of 18, Bell had been experimenting with the idea of transmitting speech. In 1874, while working on a multiple telegraph he developed the basic ideas for the telephone.

He and his assistant Thomas Watson finally proved successful on March 10, 1876, when the first telephone message was transmitted: "Watson, come here; I want you.". This led eventually to the establishment of the Bell Telephone Company, still in existence today, which introduced the telephone to the world. story of our ongoing quest to communicate better, from the first simple messages to today's sophisticated global communications.

History :

Operator mannequins, Telecommunications Museum, Madrid, Spain Historically a PBX was a company's manual switchboard. These were gradually replaced by automated electromechanical and then electronic switching systems, called PABXs (Private Automatic Branch eXchange).

The old kind were then called PMBX (Private Manual Branch eXchange) As PMBXs are almost unheard of these days, the terms PABX and PBX have become synonymous. When PABXs were built using solid state and digital components the term EPABX came into use, but PBX is still more widely recognized.

The PBX term was dominant for so long, that it is now being applied liberally to systems providing complex services regarding telephony, even if they are not Private, Branches or eXchanging anything.

PBXs were distinguished from smaller "key systems" by the fact that external lines are not normally indicated or selectable at an individual extension. From a user's point of view, calls on a key system are made by selecting a specific outgoing line and dialing the external number; calls on a PBX are made by dialing the escape code (usually 9, 0 in some systems) followed by the external number.

This automatically selects an outgoing trunk line, also called "outside line" or in Bell System jargon DDCO (Direct Dial Central Office) upon which to complete the call. This practice is becoming obsolete as number analysis systems change with modern technology - one can use internal numbers or external numbers without escape codes.

The first consumer PBX systems were for the analog telephone systems, typically supporting four private analog and one public analog line. They have the size of a small cigar box or smaller and are inexpensive.

The word 'security system' normally means burglar alarm. These burglar alarms are in the electronic form. They are generally designed to trigger whenever a certain door is opened or motion is detected with the help of infrared rays. Some alarms maybe restricted to only one type of task whereas others can handle intrusions, fires etc. simultaneously. Today highly sophisticated burglar alarm systems are available which are capable of instantly notifying the nearest police station or patrols of the break-in. Other slightly wild systems which may zap the intruder can also be bought in the market. Most of these systems can also be integrated onto cars and other vehicles.

History :

The history of the burglar systems is pretty difficult to trace. In the early days, it has been rumored that castles had almost invisible trip wires which would notify the guards of an intruder. Fact or fiction is anybody's guess. The first electric burglar alarm was installed on February 21, 1858 by Edwin T. Holmes in Boston, Massachusetts.

The first attempt to make a comprehensive alarm system was popularly known as a 'local bell'. In this type of system there was a bell attached indoors inside a metal enclosure. A key switch would turn the bell on and off. The mechanism would function with the help of wires and relays.

The key switch would be turned on before sleeping or going out. If anybody tried to force the door open with the key switch on the bell would go off. The bell wouldn't stop until the key switch was turned off. The major flaw in this design was that the bell could be easily yanked off.

After this the next attempt was by connecting the wires to the nearest police station with the help of telephone lines. This way an attempted intrusion would directly lead the police to figure out exactly where the break was staged.

These systems were popular with many jewelry store owners and high risk businesses. The downside of this system was that it clogged many telephone lines and there were thousands of cases of false alarms on a daily basis.

After this was the age of the digital communicators. These callers would place a call to the police stations and each premise unit had its own unique premise number. This technology too made use of the telephone lines.

By this method the police were accurately able to trace the intrusion and to the relief of many a police officer the number of false alarms dropped significantly. There was a way to bypass this feature as well that was simply cutting the telephone lines.

This led to the need for a backup communicator, which was cellular in nature. Today such types of digital communicators are most frequently used.

Types

If you see there are basically two types of burglar alarm systems i.e. Bells Only Alarms and Monitored Alarms.

In the Bells Only variety upon intrusion the alarms go off, these are usually high pitched ones which would instantly alert anybody in the surrounding. In the Monitored Alarm once triggered, a signal is passed on to the monitoring station.

This way official help can be called for within minutes of a break-in. Automobile security systems also work on the same fundamentals like the burglar alarm systems with both varieties available.

The other variety is the video enabled surveillance. In this kind there is a camera placed outside which monitors any movements. The user has a screen on the inside to see all the activity on the other side. Thus, he can determine if the person calling is to be entertained or not.

All the video is normally stored and can be recovered at a later date. Other hi-tech systems alert the authorities on any tampering with the device. The most common type of video surveillance is the CCTV.

The last and one of the most common types of security system is the fire alarm. This is mandatory to be installed in most of the western countries.

The fire alarm has very basic components. It is installed normally on the ceilings of the rooms and esp. kitchens to detect temperature and smoke changes.

If the temperature goes beyond a certain limit or if there is excessive smoke detected, then the alarm may either notify the occupant or may act on its own by engaging sprinklers.