1. ENHANCED PABX SYSTEM WITH REROUTING/LOGGING SYSTEM
Esther Tina Escolastico, Niña Rica Hernandez, John Alexander Rhoss Largo,
Rhett Francis Mallen, Charo Anne Marasigan, Jian Carlo Reyes,
Edsel Uy, and Januel Mikel Venturanza
V – BS ECE
In partial fulfillment of the requirements in ECE 191.2
March 3, 2003

2. OBJECTIVE OF THE STUDY
To implement a PABX system servicing the rooms under the ECCE department
The system should be able to route calls to a person’s location/room at a certain time
Signals used in the public exchange should be the ones implemented in the system
To interface the physical system to a central computer for control, administration and decision-making

3. BACKGROUND
Private Branch Exchange (PBX) replaced by Private Automatic Branch Exchange (PABX) in the 1960s
Introduction of PABX
Need for flexible telephone systems that can be expanded or innovated to cater to specific consumer needs
Automatic switching of calls between local-loop users while allowing access to (an) external phone line(s)

4. BACKGROUND Introduction of PABX (cont’d.) Ateneo scene
Automatic routing of calls to appropriate recipients while recipients can also communicate w/ the other users in the local network
Ateneo scene
Challenge: mobility of teachers
High rate of dropped and/or unanswered calls

5. WHY THE NEED?
All consumer needs and/or requirements are not always satisfied
Level of specificity that available g&s are unable to meet.
A regular PABX only diverts calls to local numbers assigned to local telephone units/lines.
End-users in a university are usually on-the-go

6. PARTS OF ENHANCED PABX A - Analog Module 1 - Local loop
2 - Loop-current detector
3 - Interface to public/Ateneo exchange
4 - Connection switches for the phone lines
5 - Switch for the different functions
6 - DTMF decoder
7 - Signal generator for the different functions.

7. PARTS OF ENHANCED PABX B - Software Module C - Interface Module
1 - Main control program
2 - Database
3 - Voice prompt
C - Interface Module
1 - Optoisolator
2 - OR gates
3 - Latches/Decoder

8. SOFTWARE DESIGN

9. SOFTWARE DESIGN
A. Main Control Program

10. SOFTWARE DESIGN B. Database
PABX system database contains the necessary information about the client like his/her name, the room where he/she is logged in, client identification code
Uses Microsoft Access database format
data control allows us to move through the records in a record set thus making the database search possible

11. SOFTWARE DESIGN
Once a Match is found, system will send Ring/Ringer signals to the two parties
Otherwise, Busy signal will be sent

12. SOFTWARE DESIGN C. Voice Prompt Module
voice prompt is only applied to Tel_5, the PLDT phone line
Instead of sending a dial tone to it, a voice prompt is put in place
Used to facilitate incoming calls

14. Optoisolator

16. Latches and Decoder
When the decoder is enabled, 3 Binary Select inputs (A0, A1and A2) determine which one of the outputs (O0–O7) will go . When enable input E3 is held LOW or either E1 or E2 is held HIGH, decoding function is inhibited and all outputs go HIGH. In our circuit, we connected the enable input E3 to the control coming from the parallel port. This control manipulates whether the decoder and latches circuit will be used or not. Enable input E1 and E2 are always connected to the ground. The outputs of the decoder are first pass to the inverters. This is because the outputs are used to enable the latches, which are active high.

17. CONCLUSION
standard PABX system simply directs calls without the use of an intelligent decision-making scheme
ordinary system, calls are simply directed to a phone unit with an assigned local number
builds on this principle by adding a database from which the central control determines the routing destination of a call

18. CONCLUSION
project integrated learnings from the subjects taken before, like Digital Design, Microprocessor Systems, Electronics I and II, coupled with new knowledge in programming languages like Visual Basic 6.0 and Turbo Debugger

19. RECOMMENDATIONS
PABX system developed in this study can be integrated with the databases of log-in systems
for further efficiency, the system can be expanded to include commercial features such as call waiting, call conferencing, call forwarding, and call diverting
system could be redesigned to accommodate more subscriber lines