Customer Premise Equipment

1. Customer Premise Equipment COMT 220

2. Definitions • CPE - Customer Premise Equipment • Correctly defined as “anything the customer connects to the network” • In practice we use CPE to mean “equipment other than simple terminals” (phones, PCs, etc.) • We will discuss mainly voice, but the arguments apply to video and data also

3. User User User Rationale • Placed between End-Users and CO connections • Provide on-premise functions • Make cost-efficient use of CO connections CPE CO

4. Different Types… • PBX - Private Branch Exchange • Full Premise Based Switching • Key System • Smaller System, usually non-switching • Difference to PBX often unclear • CENTREX • PBX functionality, but implemented in the Central Office Switch

5. Switching Principles and Methods

6. Cross-Point Switching“Space Division Switching ” 1 4 1 4

7. Three-Stage Switch From Stallings, Voice and Data Communications.

8. Time Division Switching • Each Line Card “Samples” the inbound signal (8000 times per second, each sample is taken over 0.125 msec) • While the cards collect the next sample (during the next 0.125 msec), the Time Slot Interchanger collects all samples and delivers them to the correct line card outputs • The TSI must process 8000*2*(number of conversation) samples

9. Time Division Switching TSI

10. PBX “Block Diagram” Local Switched Access Analog Phones L I N E S PBX Switching System T R U N K S IXC Special Access Digital Phones Private Lines Special Workstations Administration CTI Maintenance SMDR

11. Packet Switching? Analog Phones L I N E S PBX Switching System T R U N K S Digital Phone Digital Phone

12. Categories of Features • Features for the System User (Internal Customer) • Features for the System Administrator • Features for the Caller (External Customer)

13. Handling Outbound Calls • Call destination restrictions • Least cost route selection • Automatic redial

14. Handling Inbound Calls • Routing Calls • Attendant • Direct Inward Dialing • Handling Unanswered Calls • Call Forwarding -- General • Call Forwarding -- Busy/No-Answer • Hunt Groups • Queuing and Message Services

15. Handling Unanswered Calls • Hunt Groups • Queuing • UCD • Universal Call Distributor • ACDs • Specialized PBX software for inbound call handling

16. PBX Capacity • Traffic (usually measured in call minutes per hour) • How Many Simultaneous Calls • Processor • Total Calling Volume • Busy Hour Call Attempts • Physical Interfaces • Stations and Trunks

17. “Programming a PBX” • Moves, Adds, and Changes (MAC) • Establish New Service • Disconnect Service • Change Features On Existing Service

18. Adding an Analog Station • Physical Install • Assign Extension Number • Assign Class of Service and Other Features • Often uses a template (or “Table”) A 1234 B C

19. Adding a Digital Phone • Physical Installation • Define Feature Buttons on the Digital Phone • Define Line Appearance Buttons • Assign Extension(s) to Line Appearances • Assign Class of Service

20. Button Assignments A B 1 2 3 C 4 5 6 1 7 8 9 * 0 # 2 3

21. Button Assignments A Hold Xfer B 1 2 3 C 4 5 6 Line 2 1 7 8 9 Line 1 * 0 # 2 3

22. Extension Assignments A Hold Xfer 1234 B 5678 1 2 3 C 4 5 6 1234 1 7 8 9 5678 * 0 # 2 3

23. Extra Slides

24. Multi-Stage Crosspoint Switching - Concept