Thought For The Week
No Question Is A Bad Question!
KSU
Key Systems Are Fairly Simple On-Site
Telephone Systems Geared To Organizations
With Fewer Than 100 Telephones.
At The End Of Lesson 5, You Should Be
Able To:
Describe The Components Of A Key System
Describe The Type Of Business That Would
Most Benefit From a Key System
Explain The Limitations Of Key Systems
Key Point
Key Systems Provide Multiple
Telephones Access To Any Of Several
Lines.
A System In Which The Telephones Have Multiple
Buttons Permitting (Requiring) The User To
Directly Select Central Office Phone Lines And
Intercom Lines.
Key System Components
A Key System Provides Multiple Telephone
Extensions Access To A Group Of Single
Telephone Lines.
To Connect A Telephone Extension To A
Line, A Caller Simply Presses One Of The
Unlit Line Buttons.
Key System Components
The Concept Of Key Systems Is Illustrated On The
Key Telephone System Diagram Which Is
Different From The Diagram In Our Text.
Six Incoming
Telco Lines
KSU
Power Supply
.
.
.
12 Key Telephones
66-Type
Block
Key System Components
The Main Point To Remember About A
Key System Is That It Can Support Only
As Many Incoming Or Outgoing Telephone
Calls, Or “Call Paths,” As There Are Lines
Installed.
Key Systems Are Digital.
KTS’s Have Six Major Parts.
KSU
Line Interface.
Station Interface.
Power Supply.
Connectivity.
Key Sets (Key Telephones).
Acronym For A Key Telephone System – KTS
A Telephone System That Has Multiple Buttons
That Permits The User To Directly Select Central
Office Phone Lines.
Single-Line Key
Telephone
Speaker
2 Line x 16-Character
LCD Display
1 Line-Selection
Button
1 Hold Button
1 Line- Intercom
Button
8 Key Set
10-Line Key Telephone
With 12 Programmable
Buttons
12 Programmable
Buttons
1 Hold Button
10 Line-Buttons
1 Line- Intercom
Button
Speaker
Key Set With Busy
Lamp
KSU (Or Key Service Unit) Contains A Space
Division Switching Matrix Under The Control
Of A Microprocessor.
KSU Is The Main Part Of A Key Telephone
System.
KSU Contains The Electronics That Control
Which Line Is Directed To Which Phone.
KSU Is Usually Mounted In A Closet Near The
Telephone Company’s Demarcation Point.
KSU
Switching Matrix
Line Circuit
Line
T
Circuit
R
T
R
Line
Circuit
Line Circuit
Line
T
Circuit
R
T
R
Line
Circuit
Control
Signal
CPU
Central Office
A Single-Line Telephone Like A 2500 Set Usually
Will Not Work With A Key System Because Key
Systems Use Proprietary Signaling Protocols.
Also, Multi-line Phones Made By A Manufacturer
Other Than The KSU Manufacturer Will Not
Usually Work.
Key System Phones Usually Have:
One Button For Each Outside Line.
One Hold Button.
One Intercom Button.
When A Multi-Line KSU Phone Goes Off-Hook –
Nothing Happens Until A Line-Button Is Selected.
When Off-Hook & A Button Is Selected, The
Phone Sends A Signal Over The Signal Pair To
The Microprocessor.
This Signal Will Cause The KSU Switching
Matrix To Connect The Phone To The Desired
Outside Exchange.
Dial Tone Is Then Received From The CO.
The Phone Sends DTMF Tones Over The Voice
Pair Using The DTMF Pad.
KSU Nomenclature – A 612 Key System Can
Handle Six Exchange Lines & Twelve Multi-Line
Systems.
In A Key System, One Station Is Designated As
An Attendant Position.
This Station Rings On All Incoming Calls.
Once The Attendant Answers The Call, They Put
The Call On Hold And Use The Intercom To
Signal A Station To Pick Up The Appropriate
Line, Or Flashes A Light.
Many Key Systems Are Capable Of Automatically
Answering Calls And Requesting Callers To
Identify Which Department/Person They Want.
Cordless Key Systems
Provide Employees Telephone Service While
Allowing Them Freedom of Movement.
Wireless Transmission Is Used to Connect These
Mobile Extensions to the Main Business Lines,
And To Each Other By Means Of Intercom
Features.
Cordless Key Systems
This Type Of Technology Is Presented On
The Cordless Key System Diagram.
Cordless Key System
Hybrid Systems
The Term Hybrid Was Used To Describe A
Telephone System That Includes Features
Of Both A Key System And PBX.
A Characteristic Of A Hybrid Key System
Is The Grouping Of Outside Trunks Into
Pools, By Function Or Organization.
Hybrid Systems
Electronic Key Telephone Systems (EKTS)
Often Cross the Line Into the PBX World,
Providing Switching Capabilities.
EKTS Is A Key Telephone System In Which
Electromechanical Relays And Switches
Have Been Replaced by Electronic Devices.