The Introduction Of telephony System

in my childhood, i always wondering what telephone is made of. Why i can talk as if the person is in front of me despite their house are 2 miles from mine. then time move on..

today, i stumble across unified communication, using telephony system(PBX), look alike telephony system(VoIP - IP PBX), and some other unified communication(collaboration between existed system.).

lets we dive into the telephone system. in this title, station are referring to telephone. 

PBX

stands for private branch exchange where its a device that routing your phone from single line into multiple line inside you office. but nowadays the use of PBX are obsolete  because emerging new system.

IP PBX

this PBX using intranet / ethernet networking peripheral to route your call from outside world into your office.   for example of this system you will see at your office are not normal phone, it has data port alongside analog port. common usage nowadays in small or bigger office. 

Trunk Line

trunk line is a line that you can use to call outside world (PSTN) or from outside world to reach you. if you use that line to call, another person who wanna call you will be diverted into voice mail just like your handset. 

usually your main phone number is the trunk line.

PSTN

stands for public switched telephone network. Its a device that routing your call based on what you are dialing. for example, if you press 911, the PSTN will automatically routed your call to the nearest hospital. 

its like a switch in internet/networking environment.

Thats are for newbie, but what's there for something more? setup your pbx? 

good, now u can talk to your gf next door 24/7 for free. 

to setup the PBX, u will need:

1) PBX SERVER (for analog phone, need to buy) or VoIP SERVER (For digital phones, used pc)

2) if you wanna used analog phone, pls read this. The server must have analog port to allow in coming call and out going call. u need to configure everything in the server USING PHONES!!. The most efficient method hardware to use for analog phone is LinkSys PAP2T. this hardware configure using computer. dont worry. but the disturbing part is it only have 2 analog port which means only 2 analog phone can be plug in that hardware.  

3) for VoIP server, its only used old pc to setup the server. because VoIP are using this special phone: SIP Phone. SIP Phone are not normal phone. they are computer that look like phones. The software for VoIP is Asterisk@Home, Trixbox..

The rest is yours to command.