The present day of electronics has advanced in each and every field. The conversation between two persons sitting at a distance is not an exception. Various types of cordless telephones, intercoms and many other devices have entered the market to solve this problems. However these devices are very costly and cumbersome. The project described here is very simple and solves these type of problems to a great extent. You can use this gadget anywhere you like as it is cordless. No wiring is needed. As such this can be used anywhere and shifted to anywhere. It is portable.
TECHNICAL DESCRIPTION AND WORKING
This project has been developed and tested O.K. in our TV Engineers Technical Lab. The components and PCB used in the projects published in our books are available for sale at resonable price.
The project is an unique but complex in the field of electronics. The project has so many sections for its smooth functioning. However its working mainly depends on NAND – GATE schematic trigger IC 4093. The project has the following sub-section.
- Tone Generator
- Audio Signal Converter
- BPF Circuit [Band Pass Filter]
Whenever we lift the hand set of intercom from the stand, the REED megnetic switch attached to the stand becomes ON triggering the IC LM567. The triggering of the IC depends on the transistor Q5. This IC gererates a frequency and feeds to other ICs LM 386. The IC LM 386 produces a tune which is heard from the speaker as an alram. Whenever the handset of the other Intercom is lifted the alram stops ringing and indicates you to talk.
PRECAUTIONS WHILE ASSEMBLING THE PROJECT:-
otherwise reverse connection may damage it.
*For better responce of the project wiring of band switch should be proper.
* While mounting transistor, you should connect collector , base & emitter properly.
*Check polarity of electrolytic capacitor while mounting on PCB
* Please use resistance of the exact value as given in the circuit.
*Clean PCB after soldering, so that the component or print do not short.
*First of all check all the components as per circuit.
IC LM567 =2, IC CD 4093 =2, IC LM386=4, TRS. BC148=12, REED SWITCH =2,DIODE IN4148=18, DIODE IN4007=8, ZENER 9V=2, ZENER 6V=2, RESISTANCE 18K=4, 1K=10, 3K3=6, 47K=8, 5K6=2, 22K=4, 2K2=8, 220K=2, 12K=4, 470K=2, 10K=12, 4K7=4, 100E=6, 1E=2, CAPACITOR, .001uf=8, .01uf=14, 1mfd/50V=4, 4.7mfd/50V=4, .04uf=10, 470mfd/16V=2, 100mfd/16V=4, 220mfd/25V=2, 220mfd/16V=4, 270PF=4, .022uF/680V=4, 370pf=2, 3K3pf=2, 1000mfd/16V=2, 10mfd/50V =4, .022uf =2, .068uf =2, 330pf =2, STEP DOWN TRANSFORMER 0-9V=2, SPEAKER=2, COIL SET [7COIL EACH SET]=2SET