Rayfield Communications
2748 S. Austin
Springfield, MO  65807
417-887-1434 (fax)

Introduction to Telephone Systems


Level: Beginner
Presenter: Eli the Computer Guy
Date Created: August 2, 2010
Length of Class: 54 Minutes

Telephone Systems

Purpose of Class

This class introduces students to the basic components of telephone systems.
Topics Covered

Public Switched Telephone Network
Central Offices
Trunk Lines
PBX and Voicemail Systems
PBX Stations
Voicemail Subcribers
Class Notes

Telephone systems are not complicated if you understand how they work.
A Word on VoIP
VoIP is not a telephone system
PSTN -- Public Switched Telephone Network is like the Internet, but for telephone communication
NADP -- North American Dialing Plan -- Is the system for routing telephone calls.
Central Office -- All telephone lines connect to a local central office
Trunk Lines
Every Trunk Line has a telephone number
A Trunk Line allows for 1 incoming or outgoing call. You can have far more telephones in a building then you have trunk lines.
Incoming Trunk lines are setup in Hunt Groups. If the main phone number is busy the call is automatically forwarded to the next number in the Hunt Group
Incoming Hunt Groups are setup by your local telephone company.
Outgoing calls can be routed to use selected trunk lines. This in configured in your PBX.
PBX and Voicemail
The PBX routes telephone calls
The Voicemail system provides all audio messaging. (Voicemail boxes, Message Boards, and Auto Attendant Messages)
All devices that connect to the PBX are "Stations". This includes telephones, call boxes, intercom systems, etc.
There are 2 types of stations; Analogue and Digital.
Analogue and Digital stations have to be connected to appropriate ports on the PBX. An analogue phone cannot connect to a digital port and vice versa.
Almost all fax machines and phones you buy at retail stores are analogue. If your new fax machine does not work it may be because it's plugged into a digital line.
Subscribers are users of the Voicemail system.
Subscribers do not have to have stations
Voicemail ports are the number of connections to the Voicemail system at any one time. This includes not just people retrieving their voicemail, but also incoming calls that connect to Auto Attendant messages.
Final Thoughts
Be careful before you touch! Most older telephone and voicemail systems were administered using a phone keypad, NOT and computer interface. If you mess something up it can be very difficult to rebuild a deleted Auto Attendant or such.

North American Numbering Plan
PSTN -- Wikipedia