2B-WALKI – TALKI
As the name itself implies, you can talk to your friend while walking, moving around the park with the help of this project. Your friend or the person with whom you want to talk should have the same type of instrument. This project is miniature form of Cordless telephone and highly intertaining . The children love the project as they can use it in fun games. Also the children can play detective play like that of Comics. The project is helpful for the aged as they can talk with any body without getting up from the chair.
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 transmitter of this project transmits your voice to the other project. As such we have to impose the audio signal on any carrier frequency first. On the other hand the receiver section of the project receives the voice of other unit and feeds to the speaker. The speaker converts it into the sound signal. The band switch connected to the project performs an important role. While transmitting, the band switch remins in such a position to Cut-OFf the transistor T1 and the sound being converted to audio signal reaches the base of T2. As soon as the MORSE KEY is pressed, the audio signal being amplified by T3 and T4 reaches the aerial routing through different tank circuit. The aerial spreads the audio signal in atmosphere to a certain radius. This signal is received by the aerial of other unit. The working of the receiver is very simple and depends on the position of band switch while receiving. Whenever you speak over one transmitter, the hissing sound on the receiver of other unit reduces. This indicates that some signal is coming through the transmitter. As soon as you change the position of band switch, audio frequency is first available to the transistor T1 through the aerial. The transistor T1 amplifies the audio signal and feeds to the base of T4 via different tank circuits. Finally, the audio signal is amplified by the transistor T3 and T2 and reaches the modulator [Audio Output Transformer] opposite to transmitting action. The speaker connected here converts the audio signal into sound signal.
PRECAUTIONS WHILE ASSEMBLING THE PROJECT:-
*For better responce of the project wiring of band switch should be proper.
*For better responce use long teleshopic aeriel and coil of best quality.
*While mounting transistor, you should connect collector , base & emitter properly.
*Check polarity of electrolytic capacitor while mounting on PCB otherwise reverse connection may damage it.
*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.
PART LIST[for one set]
25K =2, 10K=2, 47E=2, 330E=2, 6K8=2, 3K3=2, 560E=2, 100E=2, 1K=2, 240K=2, 33E=2,
20Kpf=10, 40pf=2, 40kpf=2, 22pf=4, 18pf=2, .01uf=2, 1mfd/50V=2, 1mfd/25V=2, 1kpf=2, 100MFD/16V=4, 100kpf=2
TRANSISTOR BC 148=8, LED=2, MORSE KEY =2, 4 POLE BAND SWITCH SLIDE=2, POWER TRANSFORMER =2, AERIAL =2, COIL SET [3 COIL EACH]=2, SPEAKER=2