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Home Projects Telephone Related Two way Simple Very Small Telephone Exchange

 

 

Two way Simple Very Small Telephone Exchange
author: Achira



 

 

This is a very small telephone exchange attached only two ordinary Tele phones. Fully bi-directional facility with an intercom system. When a phone is in off hook condition , Exchange will detect it & send ringing pulse to other phone. When it will be picked up , the connection will be established between both phones. This will be taken place vice-versa.
 


Micro Controller = PIC16F84A
Firmware version = 1.00
Power Supply = 230 v

 

 

Power Supply Unit


 

The Power Supply  Unit.

This is used normal step down transformer (400ma) for generating three type of deference voltages & 100 AC volt for rigging.

It doesn’t provided a PCB pattern for the power supply unit. So a Vero board can be used to build the unit.

Parts List :

1.Step down transformer ( 230 V to 30 V , 15 V  & 100 V )
2.Two bridged 1 A rectifiers
3.7805 – 5V regulator
4.7812 – 12V regulator
5.1000 uf – 35 V
6.1000 uf – 16 v
7.150 ma fuse & it’s holders.
8.Necessary Wires & a wire code for AC supply.

 

Download Power Supply schematic

 

 

 

 

Controlling Unit


The controlling unit ( Exchange )

This circuit is base on PIC16F84A microcontroller. Two slimier SLIC are connected to The controlling unit. It needs to identify following connections on the controlling unit circuit diagram.

TN_SLIC_1 & TN_SLIC_2
SD_SLIC_1 & SD_SLIC_2
RG_SLIC_1 & RG_SLIC_2

One SLIC connections should be marked as,

1. TN_SLIC_1
2. SD_SLIC_1
3. RG_SLIC_1

Other SLIC connections should be marked as,

1. TN_SLIC_2
2. SD_SLIC_2
3. RG_SLIC_2

These connections should be connected as on the controlling unit circuit diagram.

 

Download CPU Circuit Diagram



Parts List :

Transistors

1. 2SC945 x 3

Diodes

1. 1N4007 x 1
2. 1N4148 x 2
3. LED x 1

Capacitors ( 16 V )

1. 4.7 uf x 4
2. 22 pf x 2


Resistors

1. 10 K x 4
2. 4.7 K x 4
3. 330 x 1

Other Parts

12 V telephone rely x 1
Necessary wires
PIC16F84A with the firmware

 

 

 

 

 

 

SLIC


The SLIC (Subscriber Line Interface Circuit )

This unit is required to detect every status from an usual telephone set for the Controlling circuit ( Exchange ). It interfaces an usual telephone to the controlling circuit. Two slimier SLIC are required for this project.
 

Download SLIC Circuit Diagram

Parts list :

Transistors

1.2SD667 x 1
2.2SC945 x 2

Diodes

1. 1N4007 x 4
2. 9 v zener x 3
3. 12 v zener x 1
4. LED x 1

Capacitors ( 16 V )

1. 47 uf x 1
2. 22 uf x 1
3. 220 uf x 1


Resistors

1. 10 K x 3
2. 47 K x 1
3. 470 x 1
4. 100 x 2
5. 47 ( ˝ w ) x 1
6. 5 (˝ w ) x 2

Other Parts

RJ 11 telephone connector x 1
12 V telephone rely x 1
Necessary wires

 

 

 

Download PCB Pattern

 

 

Downloads



Download PCB Pattern

Download Power Supply schematic

Download CPU Circuit Diagram

Download Firmware (HEX CODE)

Download Firmware (Zipped)

Download SLIC PCB Pattern

Download SLIC Circuit Diagram
 

 

Contact


Unit developed by Achiravdslnet@gmail.com

Address:

No 182 F, Pahala Hanwella Hanwella
Sri Lanka.

Tel:
+94 36 2255791
+94 36 2253556

Email :
vdslnet@gmail.com
web : www.qsl.net/4s5dd

 

 
 

 
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